Like Calista said, get yourself a pair of those knuckles. Also (and its something you can just google/wiki):
If you arent an assassin switch your secondary profession to assassin and pump your dagger mastery as high as you can (brass knuckles are daggers after all so higher attribute in dagger helps).
Get yourself a spare set of cheap max armor and affix Stalwart insignias to each piece for +10 armor against physical damage (all youll face here).
Add a max "shelter" mod to the knuckles for another +7 armor against physical damage. Add a brawns over brains inscription (for a permanent +15% damage...the -5 energy wont matter here). Add a furious handle to help speed up adrenaline gain.
Know how to use your brawling skills and be preparef to mash "standup" if/when you get knockec out.
If you really still have trouble...you can always use any of the many "boost" items to help.
* Keep an eye on Kilroy's health. If he's at low health near the end of a fight, let him die before killing the mob so he'll rejoin the battle at full health. This is far better than him dying three seconds into the next fight.
* Make sure you use the last enemy in a fight to power your skills, so you can start the next fight with your big damage skills ready. This is pretty much needed for the maghma group or you'll be overwhelmed.