My suggestions:
1) Look up Koozie's guide in the PT section
2) Make sure you actually have a decent build: 4/6/36 is good.
3) Your gear seems messed up: you need to have 2018 expertise in a WZ, 4-piece eliminator set with only the following stats: aim, power, crit, surge. Get Obroan aim and power relics.
4) Pyro damage rotation is easy: high impact bolt, assault plastique, stock strike, ion pulse.
5) Learn about, as much as possible, and master your defensive and utility abilities.
6) Realize that you are not there to face tank - keep it short and sweet: you go in, blow (or try to at least) someone up and fall back. Guerrilla tactics, baby.