The monk in diablo is very different from the monk in D&D. He's a fighter (kung fu like) not a healer.

The monk in D&D was NOT a healer. He was a fighter who had ridiculous downsides if you equipped him with weapons and some really badass benefits for fighting unarmed.

Which is why I was kind of confused why the Monk in the video had a staff.  Especially since it was clear he focused on punches and sweeps with his body.  I wonder if you get secondary skills for going down a skill tree with weapons.  It seems you get at least 1 (the ability to block projectiles as seen with the skill using the staff in the video).

Commenting on the healer bit though, it would be cool if he did have some latent healing powers.  Most other games, specifically MMOs, give Monks healing powers.  And they've already stated he's very weak.  It might be a nice addtion to give him a light healing spell.  If they don't, then oh well.

Monk is more likely a replacement to paladin.