Q:
Is Chill build reaper lame in groups?
A:
Chill stacks queue. If you apply first and cap or near cap you should rarely have downtime.
As long as you apply chill first, you will always deal damage. Chill refreshes it’s duration but it’s not overwritten.
I’ve included chill and burn into my power reaper build. Stacking 25 might solo is pretty easy, so with 25 stacks my burn and chill do decent damage. Hey, doing extra few thousand damage is not something to throw away. Specially when you consider as a power reaper you spend a lot of time in reaper shroud.
Traits like Chilling Nova, Chilling Victory, and even Target the Weak increase your damage output independent of how much condition damage you may have when in groups.
You can be effective using chill even without a maximum condition damage build so do not feel like you need to claim all of the chill stack or go home. Only Deathly Chill rewards you for owning the entire stack.