use crown of theives try and look for high life leech.. for helm ..
armor you can use durial shell
socket your reapers and put 15ias and anything else.. personally i like 15 ias and any ed jewl... i wont mention the 15/40 because im assuming if you had that kind of money you wouldnt be asking about how to keep a merc alive..
but this is a good set up.. he will get life leech both from crown and reapers.. and durials will keep him alive and good on res!!