Delerium is a good helm for your merc(best if a A2 nm def) because it has a high % to cast life tap(so your merc doesn't die). Shako is better for a hammerdin, then most any other helm, due to the high amount of mana and life that is given(based on lvl?).
If you have a delerium that you are using, put it on a merc, and use a shako for your char.
~SoD