So, I've a couple worries after going through this thread:
1) If the monsters all gang up on the paladin and just go to town... he's totally fine? End of the day, that's problematic. If all of Team Monster can't drop a single guy, defender or otherwise, then either he's too tough or Team Monster isn't strong enough, and maybe both.
Well, we have a Charisma paladin and a cleric, both with lots of optimized healing. One Healing Word can easily wipe out 80 or 90 points of damage on the pally. One Lay on Hands is about 65. And the pally gets anything that exceeds his max HP as THP. He's also god Resist All 5 and gets 6 THP every time he's hit. Of course, he also got good AC.
The running gag in our group is that the sorcerer is the monster's damage MVP.

I'm surprised that half damage on a miss is apparently quite rare. Maybe it's just the DM's choice of critters.
2) In Epic the party has a _lot_ of daily resources on tap. While it might feel logical that there would actually be less battles at epic, you will generally find that you actually want quite a lot of them to maintain good pacing.
I agree. Thing is, players often know when they're facing an encounter where the use of an encounter-buster power is optimal. Obviously, the pally saves his pain-in-the-neck power for when it will gimp monsters the most. So, does the DM just never have an encounter with some big melee brute because he knows it's just going to be maced for the entire battle? Does he just accept that it will be an anticlimactic battle? I'm reminded of older-edition battles where the gravitas of fighting a balrog is neutered by slip-sliding with a grease spell.
3) Gift of Resistance - I'd suggest that this one not be allowed to work with 'resist all' (the flimsy excuse being that "all" is not a damage type), which I assume is being done via masterwork armor. If it's just that he's collected resist items and has lots of important ones, though, that seems a good use of the power and that's fine.
See, this is an example of why I have trust issues with DragMag stuff. It's not that the stuff is necessarily overpowered, but they often seem "underthought". Seems like a no-brainer to realize how this can be used in tandem with a measly 1 point of resist all from off-the-rack legion plate. Is this what the author of that power was going for?
4) Is Discipline the Unruly (blinding), Gift of Resistance, and the other powers being used while another defender marks the targets, to create a total lose situation? It's not an unreasonable houserule to add "unless the target is marked by another creature" to many of those. Without it, they're workable (at least, after addressing point #1), but if not then I imagine a lot of epic monsters should just be leaving the field and looking to join into the next fight or come back after 5 minutes.
Yeah, there's a fighter, a dreadnought adamantine soldier. At level 25, he's got 47 AC and all his NAD's are 40 over as well. Couple hundred HP, Resist All 6, chock full of tempies--even tougher than the pally.
5) After addressing divine sanction!=divine challenge (and, again, #1), is the Hospitaler ability that problematic?
Not as problematic as I'd previously thought. It's just another anticlimactic way to neuter the BBEG--which seems to me to be enough of an issue to warrant concern. Getting locked-down by the defenders is as big of a hole in BBEG design as the action-denial effects that the Monster Vault sought to address.