I mean, seriously. Want a basic simple test to disprove this? Go to the PTR, make a level 90 Destro Lock. Pull 10 things in a level 90 zone. Try to kill them all without dying. Now repeat the exact same process with a level 90 mage, and try to do it exactly the same way. Guarantee you end up dead if you try to play a mage the same way you try to play a lock.
Just because you dont have to react exactly the same way in PvE as you do in PvP does not magically make every class just a carbon copy of eachother with different colored damage abilities. Warlocks play WAY different then Mages, which play differently then hunters.