ok, initial reactions aside, I've prayed to the sacred MEC in my binder....(sorry, couldn't resist).
Here's a little more comprehensive response.
First, there's a lot of creativity and innovation in this version. So at first blush, it seem like it will be lots of fun.
Second, here goes
MEC - Can only be used once per room, but we can use as many hp as we have. It kind of works nicely in terms of how a wizard manages their hp. No problem with this since I can boost it as much as I want. I would see using the Cabal set first and saving this for a second free action in the room. Thus, I get 4 spells in 2 rounds. I will miss not using MEC every round, but I think I can live with that.
Mage Medallion
I really like the bump to 2pts of damage per hp used. this makes me breath a little easier. Since is says "as MEC", I assume its still once per room.
Intensify - I'm going to assume Spell Resistance will come into play periodically making this useful.
Arcane Slide - Generally, not a fan of sliding spells, but nothing says I have to use this. And some people, I'm certain will love it.
Ashenne's Arch-Mage Medallion
Spell Savior - Duplicate effect of RoSS, except the cost is a whole lot higher. It's fine though.
Spell Mastery - A nice effect. Basically replicated Crown of Elemental Mastery, but with a cost.
Boost Ally - Can this be used on a Barbarian using Fury? This is kind of innovative and neat.
Anyway, yes, I do consider this legendary. There's enough here that someone should like at least parts of it. You don't have to like all of it. I would give up my Charm Necklace for this.