For me, what I hate most about subs is their homing torpedos. When a sub has his eye on you chances are you gonna die, especially mid-to-late game when there's just a handful of ships per team left alive. Once you hear the pings start it's simply game over and there's no counter play that can save you. DCP you say? OK, so you manage to defeat the subs first volley with a perfectly timed DCP, then what? The sub is pinging you again and has his torps reloaded before your DCP comes off cooldown.
I'm pretty new to WoWS. Was surprised the first time I got stealth torp'd by a DD, then I figured out how to minimize the chance of that happening. Same goes for the first time a CV focused me, it was frustrating as heck but after a post mortem analysis I can see potential methods I could've counter played. But these homing torps are different story, the more I analyze how I died to 'em the more I realize there was nothing I could have done. Totally kills my motivation to play afterwards and legitimately has me thinking about quitting WoWS before I get any more invested in this game.