My thoughts...
Use ALL toggles. Yes, all of them.
Dark uses AoE stun and AoE fear to mezze the nobodies. This gets rid of a ton if annoying incoming attacks. If you do not take both those toggles do yourself a favor and quit reading. Dark uses to hit debuffs to also reduce incoming attacks. Dark has non suppressed stealth. When they cant see you eating their friend twenty feet away you can call that defense. So Defense strategy set
Do build some +to hit and +accuracy into the thing.
Now, your big bads ignore most of that. Soooo… some of the best resists in the game. Do not neglect energy resistance. It can be built into a nice neighborhood. I have Tanked Rom on a Master Run because i have energy resistance
BEST heal in the game. Available every few seconds. Top of my head i think mine sits at 8 sec recharge. From .0001 health to 100%.
Energy Melee provides very good ST damage. Bolstered by Dark armor damage aura there is decent AoE as well. The stacking stuns might put a boss out for a few secs. like a Vicky robot in incarnate trials
since a Dark Brute is rarely killed you will win any and all DPS races.
the most spectacular tacoing of my Dark Brute i recall was a shadow shard TF. A teammate got stuck in a crossroads in a cave map with tons of big spawns all around. My overconfident butt went in. Those F-ing eyeballs ignore steath. So part of my “defense” was gone. Then…..oof. Rikti, some Nemi and a very few Longbow Wardens do the same. You need to learn the groups and know the odds. Only bet on winning hands.