I'd say you're right about Titans being the least popular option in the Crucible, but I primarily play as a hunter and rarely ever see a lot of hunters in matches; I mostly end up in games where there's at least 3-4 warlocks on each team (could just be luck of the draw). I wouldn't go as far to say it depends on your class to influence how good you are. Like I said, my main is a hunter (which is considered a really OP class) and I have some downright god-awful games where I don't even break a 1.0 KDR, and I'm getting wrecked by Titans too lol. Like some people have said on here, get comfortable with your class and fiddle around with your skill selection, and you'll get it.