zons have low defense because they do not get hit. they stay away from the action (unless your charged strike) and the have dodge/evade/(i forget the other 1) skills. So you will not need the defense merc. You will only get hit once in a blue moon. And even then, you should have put enough pts into life to survive the hit (unless it's IM). Also, when you do lose life, the above mentioned gear should give you enough life leech to leech most of your life back in 1 hit (if it's in a large crowd. ie: minions)

What is this!?! A center for ants!?