Not sure if you mistyped or I'm misunderstanding you, but just to clarify:
Might Aura will boost your offensive damage- it won't help you with negating the damage you're receiving. The only survivability help it may give is a slight boost to your life leach, because you'll be doing more physical damage. However, you should already be getting more than enough life leach from Cobra Strike.
If you're looking for some defensive help, you should pick up a merc with one of these auras:
Holy Freeze: To slow enemies around you, so that they attack slower and hit you less often.
Defiance: To boost your defense, so that monsters have a lesser chance to hit you.
Prayer: To regenerate your health (ideally with your merc wearing an Insight weapon and a Cure helm to get a fully synnergized aura)
Sorry, I'm Spanish, and sometimes I get things wrong. I use Google Translate. The aura I use on my mercenary is:
Defiance: To boost your defense, so that monsters have a lower chance of hitting you.
Because sometimes monsters hit me hard and lower my health significantly.
The mercenary has an eth forty infinity and Andy.
I'll look at the Cure helmet you mentioned, but I don't know that rune word, and I'm completely unsure of what the best base would be...
Thanks for everything, friend. You're very kind.