Here is my ranking system:
+1 star: urdar type - life regen and crushing blow
+1 star: Blunderbore / Mauler - urdar but with 75 dr instead of 55
+1 star: cursed - amplify damage
+1 star: aura - cold/fana/conv...
+1 star: TZ - higher stats
+1 star: inmune to cold/fire/light...
+1 star: 8 players - even more higher stats
Mine has atm the first 5 stars, hope to find one with extra inmunity one day. But i see not possible to find it in a 8 players game to reach the max power.