Extreme TL:DR incoming.  Check the bottom for final balance suggestions if you don't want to read!

So building on my last thread, I gathered the data on all CLs from each line and made comparison charts to show how each ship stacks up to its Tier buddies in a few categories.  I won't post the data tables since they're quite big, but you can check them out here in the excel file: http://www.filedropper.com/clprogression4

Some notes before starting:

-I do not have reload values for most of the T3 CLs. I clocked them by hand in game and believe 6 seconds is accurate enough.  There is still some margin for error though.

-I can't guarantee that all stats are correct.  I took the information as posted in the ship descriptions.  I may have made an error, or there may have been patch changes not reflected in the descriptions.

-Gun DPS is calculated as the maximum number of guns that can fire at once (broadside) times gun damage, divided by blah blah blah.  The point is that on some ships, such as the USN T3/4, or the IJN T5-8s the total number of guns is higher than how many can actually fire in a broadside, so the lower number is used.  However, I don't have access to anything past T4 on the KM and RN lines, so I can't say if a similar case exists there as well.  If anyone has information about T5+ ships having guns that only fire to one side (except the T7 USN and T5-8 IJN CLs) please drop a comment so I can amend the data.

-Torpedo damage is calculated as a the number of torpedos x torpedo damage.  No reload information is used as that is impossible to get for most ships (as they lack upgrades).  Additionally, most CLs fire torpedos on alternating sides. This means that while you may have a total torpedo damage load of X, you can really only use X/2 in a normal running gun battle unless you want to do a full 180 turn (and lose on main gun DPS in the process).  For that reason, consider real torpedo damage to be half of what is posted when considering the ship in a gun battle scenario.

-The green bars on top of the main colored ones represent the upgrade potential of that tier's stats.

DPS Comparison:

Here we see the big sexy DPS numbers, the ones everyone cries about most.  Comparing ships within a nation's line we see that:

-IJN line has extremely homogenous DPS values until the T10-11 Mogamis, where it explodes to 2 and 3 times the lower tier average.  The T9 Kita has understandably low DPS as it is a dedicated torp spam platform.  Of concern here is the flat DPS progression from T3 to T8, though.
-RN line has a pretty chaotic progression with low values at T5/6 and T9/10. This is matched by a speed boost.
-USN line has a huge T4-5 DPS gap, and a huge DPS boost at T9-10 with a fall off at T11.  That's an issue.

Comparing the lines to each other there are a few issues that require attention:

-The general T3-4 DPS progression is stagnant for everyone, for KM it continues into T5, for Rn it continues to T6, and for IJN all the way into T8.

-USN T9/10 are much much higher than other ships on their tier, and match T11 for damage.

-RN ship DPS is anemic at T9/10
-IJN's DPS values jump to a very big advantage at T11.
-USN has extremely high DPS at T5. This is somewhat offset by it having no torps.

Torpedo Comparison:

Not surprisingly the kitakami throws off the curve by a lot!  As I stated, this is not weighted by reload, and represents all torp damage at once, not taking into account having to turn to deliver alternate side salvos.  Thus if you consider the CL in a normal broadside battle scenario, torp damage would be halved as to what can be delivered. 

Analysis: There is a general lack of significant torp damage improvement as you move through tiers, and KM and RN see a decline towards the top of the progression.  When torping requires the most damage (vs high tier ships) the damage is nerfed, and when looking at the stats, the torp count is actually 6-8 for high tier RN and KM ships (except 12 on the T11 KM).  This means that you get 3-4 shots off per side, doing 6951 dmg per torpedo.  Considering the mobility, durability, and armor of high tier ships, this makes torping at high levels basically pointless for KM and RN, and not much better for the already overpowered mogamis. 

Durability Comparison:

A smooth base curve with a smooth upgrade curve.  There is once again a jump from T4 to T5 of around 7000, and there is a nonsense upgrade at T3.

Speed Comparison:

We immediately see another nonsense upgrade at T3, and a lack of any upgrade at T9.  That has to be looked at comparative to everything else though.

Defense Level Comparison:

My analysis of the overall comparison:

1) The disconnect from T3/4 to T5 needs to be addressed.  The Juneau is a bit too strong on DPS, the entire T5 gets an unecessary defensive boost, the durability gap is too large, and in most cases this is exacerbated by T3 being better than T4.  I believe this is all the result of having tier gaps at T4 that were filled in later.  The T3 is inferior, but at least gets a speed and durability boost to try and bridge the gap to T5.  Now that gap is filled, but it was filled with a copy-pasted  T3 version whose values were never optimized in any way, as clearly seen here.

2) RN and IJN T9/10 CLs are underpowered.  There's an attempt to bridge the gap for RN with a speed boost, but it doesn't make up for it's low DPS and low torp count. The T10 Mogami is also weak for having mostly useless torps.

3) The T11 Mogami is clearly OP for its tier.  A huge DPS advantage over its tier, plus the highest torp damage for its tier with all other stats beign comparable.  However, the Mogami DID actually have 15 guns, and that's quite a lot of daka!  Balancing shouldn't necessarily be just a boring DPS nerf.

4) The USN T9/10 are far too DPS heavy, and require a nerf.

INITIAL BALANCE SUGGESTIONS:

1) The T11 Mogami's OP status is important as it gives the IJN line a big advantage at T11.  But a DPS nerf would just make it the same as every other T11, and I think there should be an aim to diversify ships a bit more.  As such I would suggest dropping its speed from 38 to 36, and it's upgrade to 38.  Additionally nerf durability by 4000 points across the base and upgrade values, and reduce torpedo load from 12 to 8.  This will still make it a hellish DPS machine when played right, but should drop the margin for error and give other ships a bigger chance of taking it down.

2) The T9/10 USnNCls are outgunning everythign else, and only the T11 Mogami and Cleveland can really take them on.  Nerf the T9 Brooklyn damage by 400 on base and upgrade, and nerf the T10 by 300. 
3) Universally drop T9 defense level upgrades by 1 point and give T10s a 1 point defense level boost. This will let them tank more and stand up a bit better to T11 as well.
4) The RN T9/10 have low DPS and low torp damage, but higher def and speed.  In my experience this doesn't really help.  Boost def level to 6, and boost speed by 1.0 across base and upgrade. Boost DPS on the T9 to match the T8 Atlanta, and boost T10 to match the T9 KM CL.  Increase torp count to 12 on both.
5)Alternately, only boost RN by half, but increase defense levels by 1 point?  The survivability, combined with their speed may make it a viable alternative with a different playstyle.
6) In line with the changes to T11 Mogami, drop T10 Mogami's durability by 5000, and its speed to 36, but boost its DPS to the level of the T11 KM CL. Once again, big damage, but lower survivability for a more skilled playstyle.
7) Remove all speed, durability and DPS upgrades from T3, and transfer them to T4.  Boost T4 durability by 5000 across all lines. Remove all T4 and T5 defense level upgrades. Reduce USN T5 DPS by 5000.  Give USN T3/4 Omahas 2x3 torps (they had them in real life anyways) to bridge the gap with other lines.
8) Boost IJN DPS in T7/8 to 1500.  They have a lot of torps, but in my experience it doesn't compensate enough for the low DPS.
9) Boost KM T5 DSP by 200.  It has less torps than the other ships, but still gets far outgunned by the T5 Juneau.  Bring up the DPS to compensate a bit.

Torp balance

Somethine else that I notice is that high tier CLs have torps that, as mentioned before, have barely any value due to low salvo count per side and low damage against very fast and maneuverable ships.  Even the kita, which is a torp spammer can't really get that many hits on high tier ships as they will turn into or away from the wall and take 2-3 torps max.  And if a ship that can put out 20 torps per side can't get decent hits, then what chance does a CL with 3 or 4 torps per side have?  This is a difficult problem to address though, and my data is incomplete since it doesn't take reload into account.  However, I believe torpedoes can be made more viable for high tier CLs by boosting their speed by say 15% at T6+, and 30% at T10+. (in contrast, I think DDs should have their torp damage buffed with tier progression, but not speed)

This should make RN and KM T10-11s better, but may necessitate a T11 torp nerf for further balance.  Either way, worth thinking about.

SAMPLE BALANCE GRAPHS:
These are graphs incorporating the above suggestions with some tweaks, and others to try and bring the lines into closer balance, while still maintaining some differences for play styles.  RN is kept weaker, but has a big speed and defense boost. IJN is given better DPS at mid tiers, T9 is sped up, the top mogami's are nerfed a bit in defense and speed.  The T9/10 USN ships are given DPS nerfs.  T4/5 discrepancy is smoothed out.
Excel file: http://www.filedropper.com/clprogressionfix

That's all for now.  I hope the data is useful to visualize the balance problems in the CL lines, and input is appreciated!  I hope this generates some discussion, and hopefully some responses from the devs!

EDITED:
-Fixed embarassing underestimation of T9/10 USN CLs' DPS values that skewed a lot of the balance suggestions into bullshit territory.  Oops!  Thank you Newbie for pointing it out for me! 
-Added sample graphs of fixed values and excel file.