Raiding - Grinding to get stronger...via gear.
Leveling - Grinding to get stronger...via XP.
How are the two so different? Sure 1-70 sucks...but only when you've done it before. I loved getting my first toon to 70. My second is less fun...but still fun.
There is little difference between the gear grind, and the XP grind. My 70 may have started "end game", but I'm far from actually "finishing" BC content (full legendary gear). Not everyone wants to grind characters to that point though...most don't.
Blizzard has to keep moving the "limit" forward. Level wise, and gear wise. If there isn't "more" for a player to do, they get bored and move on.
EDIT: I also agree. Well defined quest targets are a must. If you need 5 of X item, and is has a 10% drop date...almost everyone will need to kill 50 mobs. Why not just make the target 50 mob kills? Infact, I really likes some of the quests in Outland that you just needed to kill a "wildlife in X area" quests. Especially when playing on heavily populated servers, it saves you having to search for specific mobs. It doesn't make the quest any easier skill wise, you still need to kill stuff. It just makes finding the targets easier.
They need to add more class specific quests as well. Ones that force the player to use certain aspects of their class. I found class quests were my favorite, and they could be used to "teach" new players.