I could probably have dealt with playing DPS at the endgame, but leveling was such pain. Dungeon queues took forever and I always felt too squishy to level solo through questing.
Single target damage as a prot warrior may not have been great, being able to pull whole packs of mobs and sustain myself through the fight while gradually killing them all at once felt faster and more powerful to me than trying to level a mage. Pull one thing at a time, hope you don't accidentally get an extra, burst out down, and have to rest for health and mana every few pulls.