With GM Chiv, Con Wep also grants me +5% Bonus Damage (not DI, Bonus Damage increases total damage, after all other calculations). Plus the extra DI from EoO helps with creatures that don't have a Slayer. Remember, with Sampires, the more damage they can dish out, the more they self heal. Not to mention i can actually cast Noble Sacrifice with a decent success rate to rez people. Last month i got a pretty sick Noble Sac off during a Khaldun Champ run with my guild, and ended up rezzing like 10 people with it. Was pretty clutch.