The latest iteration of DnD Next came out with a new class - the monk. Wizards did pretty well on the flavour of the monk I think but the really messed up the combat math. Surprise! No, wait, every edition of DnD has done that, so nothing new to see here...
The monk is built around the idea of using expertise dice in the same way as the Fighter does but with the addition of random immunities (Fear, Poison) and Ki powers like stunning the enemies or healing. Unfortunately although those abilities are cute they really need to be packaged along with decent beatdown and toughness to stack up and they really don't manage that here. I built a well rounded Dex fighter and a Monk and discovered that Monks do roughly 45% of the damage of a Fighter and have about 72% of the HP. When the enemy is at range the difference is even more stark.
Now being immune to things here and there and stunning humanoids occasionally is nice but I just can't see how you can justify this kind of discrepancy. If anybody asked me which character I would want for my party there would be no hesitation whatsoever - when fear immunity comes home it sure is great but the strength of a character is not in being stupendous in 10% of the fights but in being excellent in 90% of fights.
"I can stun people a couple times a day!"
"Uhhh, sure, but I do more than twice as much damage as you."
"I don't get poisoned!"
"That's great... so when you run out of HP and are unconscious, again, you can be not poisoned!"
"I can walk on water!"
"Which, when you do it, makes you do even LESS damage? Grats?"
Strangely Wizards actually seem to be kinda balanced against Fighters. I have them both doing 27 damage / round assuming 3 round fights and two enemy targets but the Wizard lasts 15 rounds total and then SUCKS while the Fighter keeps on beating down for infinity. Rogues are in the same boat as Monks, but at least their pathetic combat performance is balanced by them being utterly overpowered at Skills to the point that nobody else should even bother...
While I really have high hopes that somebody at Wizards will notice these problems before they actually launch it does disappoint me to see such poor balance choices. People enjoy having their time to shine so we shouldn't set everyone up to be the same but this goal is not served by having one person shine virtually all of the time. Having a bajillion writers and backstory folks is great but Wizards really needs to hire someone who specializes in spreadsheets rather than stories. You can have both great story and balance, they are not mutually exclusive.