Yeah, others have pretty much covered it, but I'd put DRG on the more difficult end of melee personally. Not because it's hard, per se, but more because it feels particularly punishing if you do mess up for whatever reason. The basic combo chain is so long that if you make a mistake you have to basically start it all over from the beginning, and that's before you even consider being animation locked for some of the OGCDs and having to use your share skills on others. Keeping your own personal buff up, though, is actually fairly easy once you get high enough in level as just doing the basic combo functions to keep it active pretty much all of the time (provided you don't mess up the combo along the way).

If he's determined to be a melee I would put both Monk and Sam as easier than DRG simply because if you do make a mistake in their rotation it's not as punishing to just pick back up and start again. Sure your buffs and whatnot will be misaligned but that sounds like a concern that's probably out of the range of concern for him at his current interest/skill level. I agree with the others, though, and would say that if he's actually open to any class then maybe one ranged classes would be better. I would actually suggest Machinist. It can be a little buttonsy in certain moments but you're free to move whenever and whereever. No cast bars to deal with and a pretty simple combo chain. Your buffs also general line up very well normally so it can almost be a "just hit buttons when they're off cooldown" style class.