Your doing it all wrong, I'm a level 35 mara, I don't have trouble leveling and I dont use Quinn. First thing understand the way they made the game, you will always be fighting multiple enemies at once. To take less damage you must kill them ALL quickly.
First thing wrong pop Cloak as soon as your health his < 90%, retaliation will get it back.
Next thing use Ravage then use SMASH -- this move stuns all the enemies SO THEY CANT ATTACK.
Third thing, get rupture up immediately so you start healing yourself sooner.
Those are the main things, also you might want to switch your talents up
tier 1 : Move 1 point into QR more smashes = more dead and stunned enemies. You want to pull another point from somewhere up the line to add to this too. I just dont mind 66% in Enraged Slash.
Tier2: Rupture will be come a refresh-able spam-able slow. I pvp alot so this is nice for me.
tier3 : cool
tier4: I have 2 in shortfuse and 1 in close quarters and none in subjugation, Why?
shortfuse = should not have to explain. ( IF you dont get it switch classes )
close quarters makes Charge a rage builder now and flipping is always cool, but under 5 yards you should just run.
subj: I dont know what obfuscate is and we have extra interrupts like choke and smash.
That should do it. ALSO screw Quinn and get Vette some better guns. Seriously look at her damage....