zmeckancek wrote:1a.) does the target only take damage from 1 missle (because of the 'next delay')? So basically increasing the number of missles only improves the AOE coverage and not the single target damage?
Yes, missile from the same skill will not be able to deal the damage before the delay expiration from the previous missile.
zmeckancek wrote:1b.) will increasing my cast speed at a certain point actually lower my DPS (because, for example, every other cast won't do any damage, because the next delay wont 'reset' fast enough)?
No, you can't lower your damage output, though there is a point of "saturation", after that point your damage won't increase further because of the next delay.
zmeckancek wrote:My arcane torrent tooltip damage on the character sheet is much higher than any other spell on my other chars of comparable level, and yet the actual damage output of arcane torrent is the weakest by far, even on full mana bulb.
You can't compare the raw damage numbers from the skill description, if skill and its synergies (from its level or other skills) does not provide you a significant damage boost, generally speaking it might point you out that this skill is just inferior to others.