SN BB6 sux in GB and in HA too.
It's a ship slower then kaiser, firepower of a kaiser(tested on live server), has high angle guns(the one thing that makes people dislike amagi).
Why use a P24 when you can use a Kaiser that has space for more then 3 T5 scout, waaaaay better AA, better range, more speed, less gun reload and not much of the high hangtime crap.
Against the rush of AW ships, you will start hitting a AW ship at 33-34 degrees thanks to it's high angle guns and low speed, so it's crap against armored ships to, unless you get a lucky max angle hit.
Thanks to it's high angle and speed, you can't expect to hit anything or slingshot like a Nebby or even an Amagi in a line battle. So yes, the SN BB6 is crap, it's bad in a line battle and against AW rushes and against compact & fast moving ships. It needs more firepower and scouts.
The BB5 is a BB4.5. It's slower than the other BB5, and has the second lowest range. In GB it will probably outperform a H44, but I still find it relatively a crappy BB5. It needs more range in both guns, the triples should be the same as that of H44, the quads like SY.
The BB4 is also a BB4.5 with the 16"guns, and a BB3.5 with the 12" guns. The 16" has too much range and the 12" has too little range. They need to give the 16" crappier spread and the 12" more range.
The only good thing in every SN BB is it's awesome spread right now.
Also, the BB3's aren't awesome either, after the displacement increase for the IM, it's well balanced for a BB3. The Kronshtadt on the other hand, comes in the same category as the Hood.