Try setting free for all loot. Then just loot on your main, and when you see a quest item, have your alt loot it. So your main gets quest items last, that way you make sure your alts all get items they need. Quests are VERY good exp and money, but try to shy away from collection quests, since the effect you already noticed. You should probably do them until like 6-10, but if you really don't want to, go to a new starting area. So you can do easy quests in the area you are in, and then go to the other starting areas and do their easy quests.