OK, so I have been playing Vanguard for some time, and I have two conclusions:
1) it is bloody difficult
2) it is bloody amazing
The key, as I have been warned, is to treat it as an oversized cruiser: get in close and blow up anything smaller than yourself, run away from anything the same size or bigger. Took me time to apply it, but suffice to say: I am not going back to the traditional long-range slugfest battleships as my primary ship type (I might use them if I feel like playing a game while half-asleep, though). One (the only, in fact) problem I do have with Vanguard is its artillery setup: eight twin turrets combined with very narrow turret traverse overall mean that I can only use two of the turrets if I do have to engage a battleship. That being said, since running away is usually a better option, that may not be an issue (I did kill an Iowa in Vanguard, but that was a) a bot and b) left me hanging onto last bit of health I had, so I had to spend all the repair consumables before returning to battle).
So what are the best cruiser-killer battleships in the game? I am thinking that French late battleships might be good, as they are fast, and based on the historical aspects should be overall similar to Vanguard (Richelieu had 8 15-in rifles, but in two quad mounts, and was quite fast). Other than that, I was told that Japanese Kongo is similar, though so far I could only afford to get Myogi; Kongo will need more XP, but that will come when it comes. So would it be better to switch to French or Japanese battleline? EDIT: I am guessing French, considering Japanese "endgame" is the Yamato.