Avoid collection quests like the plague, unless you need one or more chars to catch up on others, and if you don't mind spending hours doing them.
The ONLY time I do collection quests is if either a) there is an abundant supply of the mobs and I need to get more XP for one or two toons b) I have multiple quests in the area which require killing the same mobs and only A and/or B if c) the item has a 100% or near 100% droprate.

There are many quests which say "get 2 of these!" and you're required to massacre entire zones to get a single drop.