70-80 is horrible though... I wish Blizz would add some feature to reduce the levelling requirement on accounts that already have a max level toon on in.
Please, god..er... blizzard, don't make leveling any easier than it already is. I don't care what the reason.

Yes, collection quests are harder than kill quests, but remember, you get 5 quest turn ins just for killing 15 mobs instead of 75 mobs if you single boxed them all on non-collection quests. You get multiple credits for kills on "plant the flag in the corpse" crap. You get 5x the gold on group quests for killing one elite that took 2 volleys of lightning bolt instead of the normal one.

It's easy to look and complain about the disadvantages of a situation, but when you take into account the advantages, it's not really as bad as it seems.

One other thing to realize is that even when you single box (this was pre-RAF), a majority of your XP actually got was from mob kills. You "had" to grind during different stages of your leveling despite best efforts to keep up with xp. (Unless you instanced or only lvl'd on rested) Vanilla wow zones didn't have the 100+ quests in them to get xp from. Outland and Northrend are simple just for that fact.