I'm afraid that this strategy wouldn't work, as you can not switch talents in the middle of a challenge mode. What you start with is what you have to use for the whole thing. In my experience with CM's (which is admittedly from getting golds in MoP, haven't started getting golds in WoD yet), it's the trash pulls that are often the tricky part. This is where groups are often the most stressed because you're often chain-pulling as much as the healer's mana will allow to cut down on time. I would think that defile+gorefiend's grasp would give you the most bang for your buck in those situations an