This is why I found borderline asinine Lor'themar's decision to bring Alleria to visit the Sunwell. But I guess we had to witness the next power creep happen in real time, so there's that.
L'ura was just a Naaru, as might as they are. Decimating a city in WoW's scale is not much of a feat, and the parallel with the Demon Hunters might not stand (although really we just don't know whose demons get consumed, we kill a named during DH's intro quest), but the others do.
Then again power levels are as high or low as Blizz demands it. Saurfang axed 25% of Malfurion's hp, and Malfurion should be untouchable by anything mortal given how divine he's increasingly becoming.