The thirst unending in the blood elf starting requires that you use your arcane torrent on a mana wyrm, yet no matter how I use it against them the quest won't complete. I've used both in and out of combat and when they were at very low health.
I was testing it, you must use "Mana Tap" (20sec cd) on the Mana Wyrm, not "Arcane Torrent" (2min cd). You have to make use of it on 6 targets. Your version would take 10mins to complete that quest with a timer of 2mins between each spell;)
I was going to report that bug, but while questing in the area...if you just use the racial spell on any other mobs other than Mana Wyrms, it will proc your quest....It's warmane, and that it is out of the ordinary made joy to me actually, 'cause we all know those quests all too well, this way you get to explore and try to get around a bit... It is bugged but still doable