I had enough trouble with a pack of ... the large guys you meet quite early in Act I - unburied corpses or something like that, which were ... Vampiric and reflected damage.
But actually, I already dislike the elite mobs. The only good thing about them is the loot. What I really like is fighting large groups of normal enemies. I think 40 or so is the most I've encountered at once. That's the problem. You meet smaller groups of stronger enemies, and ... you sort of notice how weird the decision to make health globules drop and give pots a significant CD is. I've been playing D2 for the past few days, and having quick access to your potions with no CD doesn't make you invincible. You can only carry so many ( your inventory space being far more limited than in D3 ) and they don't heal you instantly. But they do allow you to stay in the fight. In D3, if you get cornered by a strong enemy and you've used your potion, you have no choice but to kite them around while waiting for the CD. That's ... just plain bad design.
The gold thing is another thing that ties in with the loot thing I complained about earlier. It really is true that a lot of the game is built around the auction house. It's evident in the fact that you don't really earn gold from vendoring items, and the cost of a single potion being, well, as significant as it is. Instead of going out and killing enemies for good loot ( and occasionally gambling ), you go out to kill monsters for regular loot which you use to make your own crafted gear. That makes no sense.
Unless, of course, as a cynical person might suspect, Diablo 3 is nothing but Blizzard's pyramid scheme, based around the idea of getting people to use the RMAH.
But who could think that of a corporation? As we know, they always have the consumers' best interests in mind, and would never resort to making their game in such a way just to make a few lousy bucks.