Seeing that the game has two modes, namely PvE and PvP, what works on PvE might not be working in PVP. Let's say for instance, Ley Lines. Do you think a BLM can successfully cast their spells in it? Another would be the very famous 2x fell cleaves. With holmgang, it's very impossible to dodge it. Now this is an issue that a tank does way better than a DPS and would greatly skew the playerbase who just wants to experience the game to its fullest. If not addressed then the already dying PvP will be as good as dead. If worse comes to worst, an ability will have its own mechanic on both modes which to me is just a lazy solution to the problem.