I have levelled several teams 60-80 now so will give my thoughts. Dont skip all collection quests imo just the ones the involve killing someone ie in HFP do the quests picking up metal and wood but skip the blood one.

If you know that you are going to be grinding a certain mob that drops a kill reward you may as well do the quests even if you just do it on one toon - you can cycle who gets the kill reward so all your toons stay roughly level. eg I like to aoe down the buzzards in HFP but I am not going to go out of my way to make sure I collect all the feathers on all of my toons. I may collect on toons 1-3 then next kill quest eg Naga claws I will get on toons 4,5.

I definately recommend AV to fill in between quests. Its good XP breaks up the monotony and teaches you new tricks without feeling you are letting the team down for poor perfomance. I did not bother with instances 60-80 for my alt teams though.