The easiest way I found to do this achievement legit is in arena as Neith. At the start of the match, run over to the enemy teams mana camp. Nine times out of ten there will be three to four people waiting to kill the camp. Run into the middle of them the back flip back out. Then when you land fire your Spirit arrow onto the broken weave that the back flip created. The Aoe should hit at least three people waiting for the camp to spawn. Achievement Unlocked!