For magic heavy parties there's only 2 real options. Take the trap damage or Telekinesis from far enough away that you don't take any damage. You'll need Earth Master magic for option B. If you do option B you could just not open any chests till someone has the spell. Actually the LV 15 Necro starts out with Master Earth Magic.Trap damage is very random. I think the higher the treasure class the higher the trap damage will be. As you progress trap damage won't be so bad but in the beginning 2 traps can kill any Necro. Perception is suppose to help but with how random trap damage is I'm not sure how much it helps. You'll want at least on character with basic perception so they can pull item out of trash heaps, fireplaces etc.
I'd still depend on soul drinker and resting/temples for all your healing. The LV 15 Necro can be recruited as soon as you reach ravenshore and he's already a master dark and earth magic user. Do your necro promotion quest asap and you should have one member with soul drinker pretty early.
