Bruiser is actually my favorite mech!
Don't try to rambo with it--it's a team player. if you're looking for a mech that takes up all the kills and is the MVP/high threat mumbo jumbo, best you pick a different mech. Bruiser is kind of a jack of all trades master of non-mech--it's meant to back up other mechs in their roles, whether it's suppressing fire with the hellfires, up close damage dealing with the vulcan, mid range skirmishing with assault rifle, and generally drawing aggro with it's ability. It's incredibly difficult to survive alone, and it works best in a group--more so than other mechs.
The trickiest parts about the mech are likely the hellfires and the ability.
With the hellfires, half the time you won't even fire it--it's good for keeping targets suppressed without actually shooting. Lock onto someone and if they duck back into cover, you did your job. If they don't, well, lay it on them. Win-win situation.
Up close it's a poor man's rocket shotgun, but if you time it right it's added damage. More often than not though, stick to just using your primary in a close quarter situation--if you can't use the hellfires effectively in CQC it's just wasting heat.
The ability you use not as a rambo mode but more as a counter. If you're good with it, you can use it to block when an enemy is alpha striking you or if there's a secondary attack you can't dodge. Being able to mitigate high damage attacks like that could given you that extra health you need to come out on top in a fight. You can also activate it when you're trying to retreat, and it works the same way. The best part is that it recharges relatively quickly, so you can use it quite often comapred to most other mechs.
In sum, stick with a buddy and try to complement them. No matter what they are, if you know how to use your bruiser you will complement them well. Give it a bit of practice, and you might find he's a pretty chill guy.