It's changed so AC doesn't exist, and is replaced by Reflex saves.

Now Reflex saves are the God Stat. That needs to be mitigated somehow, either by nerfing Reflex into two separate categories or by buffing Will saves (Fort doesn't need a buff since it runs off of Con, which is already a big deal).

I think this misses out on iterative attacks (play below level 6, problem solved), and the "medium" progression is terrible. Maybe embrace the loss of evenness and just make it 1 + 2/5?