Whenever you can, run attack both minions and leaders, however you'll want to be carefull against ranged leaders as they can predict your attacks from miles away and will most likely counter you, so use your Dire Wounds special attack instead.
You have no health. You will die. Learn to dodge and counter attack. Doom Child is your worst nightmare. Run.
In order to take away 80% of enemies health, get the skills; trauma,scalpel, and second opinion. Then when you find your unlucky target, use your rally for the 300% damage boost, then use crippling blade,after that do a running attack, then use dire wounds. All in quick succesion. The best weapon to do this with is the tactical sword with infector mod for crowd control.
Use operate in isolation to your advantage, if your on low health, or see someone about to use an ability, graple the nearest soldier and be invincible.
All your abilities are for killing leaders, so pick leaders or lieutenants out from the croud, and do running attacks into the group aiming for leaders, or after you regen your abilities do step 3.
With tenblades health, running into a group of enemies will get you killed fast, you should stick with your mates, and loot, but you should always be the "entry fragger" or the person on the front line so you can quickly execute step 3.

(As a little end note, crippling blade does not pick out leaders from the crowd too well, so try to get a clear line of sight before throwing, also if they're is running sidways, and are a meduim distance away the blade with likely miss them.).