I would and it wouldn't have to have nearly as much stuff as the first poster listed. Just some good solid content which I could use and I wouldn't even be all that picky what kind of content. Just something I could use.
Putting into your wish list something vague like "class balance" is a no win situation. What is balanced in the eyes of one person is not balanced in the eyes of another; since many people seem to define balance as meaning they have the upper hand. Everyone can't be given the upper hand. So they will never achieve class balance in the eyes of the majority of players, just like no other MMORPG has achieved class balance in eyes of the majorities of it's players. There are other similar no-win situations in that list.
Ok, if an expansion doesn't have a really huge list of features it should be priced accordingly (regardless of game).$50 would be a pretty big expansion for any game. $20 would be for a lot less and might be more feasable when you remember HZ has about 3 devs working on it.