On Kolagarn, there's a very simple way to get the "With open arms" achievement (not killing any of the arms).
This is a bit harder in heroic, since there are 3 people gripped at the same time, but in a 10-man you only need 1-2 holy priests.
The trick is to guardian spirit the person in his hand. This person won't die even if you don't deal the required damage on his right arm, and Kolagarn will be slightly bugged (he'll keep this player in his arm for a LONG time, preventing him from gripping other players). All you have to do is to keep this person alive (not much damage in 10-man).
We managed to get this achievement with everyone alive using this.![]()