Having all T4 ships my experience thus far is that the BB yields the least XP/match yet requires 150% of the other classes to upgrade. It's just tiresome for no reward comparatively. It's not like the extra 50% XP translates to a 50% better ship. Either more XP needs to be earned by BBs or the same XP to upgrade as DD and CC. Also the precision needs some improvement, getting 2 hits at 10km feels like i won the jackpot, due to hight spread, the other ships are alot better in that regard.
In many ways the BB actually feel weak, but with the latest increase in part destruction, as cannons and rudders, it seems to do better in that regard. I also believe the armor actually has some effect now. I'll leave most of the balance discussion out of it, except that planes seems to be impossible to shoot down (less hp/plane and some spare at CV?) and flight torpedoes dropping at like 200m is impossible to dodge.
/Y