I'm really not sure what that system of theirs is supposed to solve.
It stops the tediousness of having to walk back to the previous "safe resting spot".
People will get through dungeons spamming spells from replenishable levels, wait for boss and unload dailies on him. People who could't still would run back to town and rest to get dailies back. We mostly did the same in every Vancian game out there. The only difference is that mages won't need to think about managing low level spells now. It's like trying to teach us fools how to spend our resources. Why can't fighters and thieves have their own moments in gameplay, and mages - theirs? Why everyone must perform equally in sense of number of actions per combat? o_O
But you are not spamming spells. Like the
J_C Matt video: Party encounters a fight. Level 5 Mage casts 1 fireball. Then notices the party could really benefit from haste. Casts that. Then one more fireball. That tier level of spells is now locked out. Also the lower level spells are the same way. You don't spam them, you can only pick a few then they are locked out. And then the higher level spells come into play. Cast them now, and then have to wait until that next rest area is found, or save it.
That system is interesting (at least to myself). It certainly is going to need some tweaking, but it could be interesting.