I think a Monk needs to gain PRR and MRR as they level up, as a class feat, so they can keep up with the other melees near and at endgame with cloth/nudism (in any stance). Make a nice, healthy +30MRR/PRR a more attractive level 20 Monk automatically granted class feat. As incentive. Because dr10/epic is
NOT. That way you can keep in line with lore (scaled to DDO) with the Monk 20 DR feat. For the first time.
Don't make them spend AP on it unless it's going to be a really big bump.
On a more realistic note: Monks on Earth, in this world we live and breathe in, have greater natural resistances, saves and damage resistance and automatic recovery than any other melee fighter I've seen, read about or met. Sure folks know field medicine and often use it adeptly but Monks are on another level entirely.
Monks can Trance and walk over coals that boil fat and fry skin in seconds,
meditate in boiling oil that would instantly kill a non-Monk,
meditate in sub-zero weather that would kill a non-Monk and punch
with the force of a small automobile up to 6 times per second while weighing less than 120lbs. Even a raging barbarian couldn't put that much force out with a two handed weapon weighing what a Monk does. To top that off, the Iron Skin ability allows them to prevent Piercing and Slashing damage entirely (focused Qi).
For every bit of additional mass a Monk in DDO has, add to the amount of resilience and brute force said Monk can churn out in addition to these facts presented. Then, because Monks are Psionic in nature, well... you see where I'm going with this. More Monk levels, more Psionic based power growing in the Monk to suit the Monk's needs. The Henshin Mystic does not use arcana per se, it is Psionic.
Then with Monks... "Do not pollute the pond." Some Monk abilities simply discontinue upon multiclassing. Others dilute. None remain constant.
Monks are
scary powerful in real life and many can use any weapon with expert proficiency, even
furniture and appliances.
On a side note: I'd like to see a Figher 20 automatic feat called "Bushido" where they deal 1% more damage for each 1% of HP they have that is less than their maximum.