From what I watched Pyro starts off slow and then gets really good in the late game.
I'm running devastator and just hit level 22 last night solo. Gear and mods mean a lot in this game. Also, there isn't one set of skills that work for everything. I noticed if I'm going against beasts I switch up my skills differently than if I'm going against human type enemies.
And unlike in Destiny, Devastator really is a tank. I can run into a group of enemies and keep myself a live and healing constantly with the right load out and if I die it's on me and mistakes I make.
Game is great and I hope to hit 30 by Sunday.