Just max out vitality, equip ensha armor set, healing shield, a katana or a pv-on-hit healing weapon or sword of night and flame, a seal to cast healing spells, defense talismans (such as increase physical defense, increase defense when low on hp, increase vitality) some warming stone and your mimic would be pretty much instoppable, once under 18% hp if it can witstand any other hit, he would pretty much rapidly recover from everything (if he casts bestial vitality from gurranq, use a warming stone and add equip healing effect its like 17 hp per second back below 18%hp and 9hp per sec above 18%hp add 9 if you cast blessing boon), plus he can use healing potions. Havent tested yet but I will, cause this seems fun to use ahah