From a Blizzard Developer on the issue of auto attack:

"The monk not having auto attack was controversial around the office too, we are not even 100% sure the monk will keep it. And removing auto attack for other classes will just feel like a huge change. We do crazy things on new stuff, not on old stuff. There are some downsides too - if a monkey has 5hp left they have to wait to push a button again were as a Rogue would just kill it with its auto attack."