By Fenrir.Calamity 2011-07-25 00:27:13
I for one like Killer Instinct for certain scenarios. It is extremely situational, but you do have to remember, in addition to giving you and your party a killer effect, it also enhances your damage towards the affected mob by 15%. In addition to that, you gain further damage increase from the effect on the af3 body, as well as some -DT.
I'm not saying you'll use it often, but it does have it's uses. After the update, it may be a good idea to put merits into Affinity, but for the time being, capping it just feels like a waste.