Agree with +4 weapon and +2 armor, but i have been trying around a little, and realised that a +2 helm isnt bad at all (if its the right one)
My vote goes for the 'Delirium' runeword (gives loads of def, +2, and best of all: chance to cast confuse!!)
with the chance to cast confuse (i think its 13% or something iirc) the enemies will mostly start hitting each other and the merc will be able to keep hitting them, triggering the confuse all the time. As a result, my merc doesnt take more than a couple of hits at most, before the monsters focus on each other. In addition to that, you will have xx skellies too, so the relative chance the merc will get hit is rather low. And you will still get better aura from him because of the +2 skills!! :thumbsup: Also, the merc will have quite good life regen, so he is back on full life pretty fast.
As a bonus, the confuse-radius is quite big, so it will also affect nearby ranged units, preventing them from shooting past the skellies hitting you.
Summary: Delirium makes a good work keeping merc alive, and still adds the +2 skills. Though its a little more expensive than crown of thieves etc, but still worth it imo.
Hope you think this idea isnt too bad. Works for me :lol: