Suggestion: Making stamina fun to use...
A few ideas I have for making stamina a more enjoyable game mechanic...
1. Chargeable Actions
Imagine pressing the key assigned to cast Fire (let's say it's the "2" key). Instead of simply pressing it once, holding the key would charge the action, causing it to consume more of your stamina bar in exchange for more potency from that action (more damage dealt, maybe more healing done, etc.).
The current stamina bar shows the selected skill and the amount of stamina the skill will require. I would imagine that, as you hold the key, you would see the amount of stamina that would be consumed by the action increase (with a possible cap). Release the key to add the action to the queue.
2. Combo Actions
It would work somewhat similar to a battle regimen, except with other potential benefits...
Press a key to add actions to a combo list (probably with a maximum of three actions). After placing up to three actions on this list, press that same key again to combine all added actions for a special type of attack that would consume your entire stamina bar (the bar would need to be full before the attack will go off). The effects could be similar to battle regimens, or it could simply execute multiple actions at once.
For example, a conjurer queues up Shell, Protect and Stoneskin. Upon activating the combo, it would cast all three spells at once, thus saving a bit of time when it comes to rebuffing (naturally, there could still be a casting time for this) at the cost of using all of your stamina.