While I agree that being pissy during a DG is unwanted behavior, so is using gameplay tactics that slow down the team. Which is why I'm guessing the BLM was understandably upset. Seeing as BLM's are built for AoE, to render him into a solo DPSer just so the WHM can throw some solo DPS as well is far from optimal. Playstyles are different for everyone but when you impose a very weak strategy I can understand why other people will get upset.