There's not a single tier of ships in this game that are perfectly balanced. The best examples of semi-balance, are BB6, 5 and 4; although that is purely in my own opinion.
The lower tier ships have been changed significantly with the BB1/2 patch in 2007/8, but there were problems they could not solve with the knowledge they had, and there are definetly some problems in the DD-BB2 range.
BB3/4 and AA guns were touched upon a few years ago as well, and brought much needed balance to these tiers; although again, they lacked both the knowledge (APHC to be exact), to completely balance these tiers.
Since I'm not familar with the CV patch, I will refrain from commenting on the CV mechanics patch.
The introduction of the French brought in a few more terribly balanced ships, which was put off for some time, as submarines were the bigger concern at the time I believe.
With the introduction of Soviets (which in many aspects, I balanced a significant amount myself during the original introduction before the MN-SN patch), another set of inbalanced ships came in. Luckily, at this stage, we figured out one of the more important aspects of damage absorbtion; although too late to make a different to the patch itself.
The MN-SN patch was better organized, although the lack of resource and time eventually left some ships with (in my opinion), temporary fixes instead of permnant fixes.
Since I took a break from NF after that time, I cannot comment on Italian introduction and Italian balance patch. (athough they seemed to be as broken as MN and SN during their introduction).
With recent fixing of rental ships, the next balancing project that is ongoing is the new EBB project, which aims to fix certain issues with current EBBs, and to make the introduction of the new EBBs less damaging to the current balance.
After the current project, I do not know what will be next. Some of my educated guesses include another aircraft patch, another SS fix, and some BB5 changes.
Advantages and disadvantages wise, it's hard to find a comprehensive list right now. But I can assure you, there there much much more pros and cons to each nations than what you've listed there.