I agree this is a big problem, and I don't think reducing the DL is sufficient to fix it. I think (always thought, before seeing it actually) that the solution is to go back to a monster distribution much more similar to the traditional one. With goblins in the deep CoC and all that.
DH was always my favorite place in ADOM, and its charm was that you could maybe have a clear passage, or maybe find a couple of really epic monsters out of your league. Sometimes you could outwit them and even kill one, sometimes you would die a gruesome death.
If you reduce DH to DL 30 what you will have is lots of very powerful (but probably not epic) monsters but that's not the charm of DH.
More in general, if what you link is going to be the typical layout of a deep CoC level, I think the game will be more monotonous and less fun than before. A large part of what made an emperor lich or a greater titan epic was their rarity. If people move around killing greater titans left and right in the deep CoC (and they will - if the deep CoC is now too hard, people would just have to scum more), they will no longer be epic, they will be routine.
I think a much, much slighter change in monster distribution would have sufficed - e.g. doubling the relative frequency of monsters within 5 DL's of the dungeon's DL, leaving all the others intact (which was more or less what JellySlayer initially had suggested IIRC).
If the current model is going to be used as a base anyway, I think the largest disbalancing factor is the fact that rarity of monsters that are much below the dungeon's DL is dropped almost to zero. Yes, I know, some people complained about goblins in the deep CoC and all that. But to make epic monsters epic and not routine, to make those levels feel varied, to keep the mystery in places like DH (will a highly powerful creature be in the next room or not?) you need to have that. Maybe somewhat less than before, but I have always thought we do need goblins in the deep CoC.