If anyone hasn't seen Mr. Happys video or attempted Sophia EX yet, during her add phase, the Paladin uses Infusion which is a line based AoE that follows the target, getting hit by the AoE seems to apply the zombie debuff. Now this is where I'm looking for clarification, it seems those who watch Mr. Happy, believe that the entire group needs to stack in the AoE, while what I have encountered in every group I've been in, we let the targeted player get hit by the AoE while the rest stand behind the Paladin.

What is the way this mechanic is handled? It's seems to have caused some stir among some learning parties as what is the proper way to go about this?