The basic loop is:

- use abilities or fight to kill some stuff
- retreat to heal and use total shut-down to cool

That means a lot of the time I'm just waiting around. I know you can cut down on the wait times by reading more of the books, but... ideally upgrading abilities should make you feel more powerful, not less inconvenienced.

I played a game called Frayed Knights recently. It had a different way to handle battle-weariness. In it, you have what I believe was called the Exhaustion bar. Essentially, this would limit the amount of stamina recovery that was possible until you go back to town to get a good night's sleep. The more abilities used etc. the higher the exhaustion climbs until you become pretty useless.

Now I don't know if this could possibly be implemented here [anymore] but the idea is if you allowed more abilities to be used in one go (so much slower increasing of heat) with a steady creep of this "exhaustion", you could have this basic loop repeating less, while emphasizing things like healing etc. potions and teleport beacons a lot more across more of the game, not just arena fights.