In my game humans are controlled by a race of super sentient beings.

To the humans, a man who has a device that shoots plasma is a wizard shooting magic bolts. They are too unintelligent to comprehend the technology.

Anyways...

Lets say these magical devices are powered biologically. They drain stamina.

When stamina is depleted, health begins to drain.

Stamina is regenerated through rest, food, and time.

In addition to magic, stamina also fuels melee and ranged attacks.

Does this sound like a sound concept?

If you combine both resources, you made it a lot more complex, complexity which demands a lot more of concentration of the player. Eg. the avatar is low on health and stamina, you concentrate on a combat situtation and fires off a magicblast, suddendly the avatar is dead, because you drained all your stamina and all, or atleast almost all, of your health. This kind of situtation would be very frustrating.

The frustration can be lessened by having visual cues so that the player won't be surprised by the situation. Also, if players health and stamina pools are quite large, battles won't be over in 5 spells (my biggest pet peeve in current games) and a player will always have the option to call it quits when health becomes low (run away while you still can survive a few hits to the back).

Many people like to plan and it is easier to plan an action if the rules aren't too complex. A very simple, yet effective planing is, to hit the magic-blast button all the time, it will fire off once you have enough stamina, thought on a very low leve, it is still some kind of planing.

It's kind of like the nuclear option in a battle. If you really must continue fighting to the death to achieve a bigger goal then sacrificing your current avatar's life (or just when you are out of stamina but your opponent is almost dead).

If you combine complexity (think of chess) with fast reaction times (think of realtime combat), then you will have a very low frustration threshold. Remember that many people play games to relax, to have some fun and don't play it to feel exhausted like after a 1vs1 SC2 ranked match.

It won't be that complex. Stamina and health pools will be large to account for permanent death.

Not every victory or defeat results in someone's death. A victory where the enemy retreats is just as victorious as one where you fight to the death.

Game mechanisms will need to be in place to allow for such a retreat though.

I think you are correct to assume that your typical keyboard pounding two ability spamming crowd will probably not enjoy my game.

There are more complex aspects of the game I have not covered like city building and industry too.

This game is more appealing to the types of players you will find in eve-online or shadowbane (closed, a large core following has built two private shards by reverse engineering the server).

Its just a hobby project so I am afforded the choice of making bad business decisions .

If you combine complexity (think of chess) with fast reaction times (think of realtime combat), then you will have a very low frustration threshold.

It's really not that complex. The way I'm reasoning it, the player would get into a battle, drain their stamina, and burn some HP. Supposing the UI isn't terrible, they will realize what they're doing and form a heuristic to deal with it; namely, keep stamina low, but not empty. If the game is as fast as Quake, this could be a problem, but if it's a bit more tactical (like EVE Online, to use DI2agon's example) the player has more time to think about... well, tactics.

Turning to DI2agon, the universal rule of game design applies here: make a quick-and-dirty prototype, and see for yourself if it works. Like in science, talking about how it would be will get you so far, but you're not really a scientist until you test your hypothesis.

Honestly, what I'm more concerned about is that this system isn't complex enough. If magic, melee, and ranged attacks all drain stamina, then what differentiates magical attacks from the mundane, apart from cool particle effects? As for the setting, a fantasy universe with godlike beings who have sufficiently advanced tech is a great idea, but how would you get across to the players that it isn't magical to them?

That idea with draining life is not too much different from what already exists e.g. in Ryzom, and if you leave out the fact that Ryzom was a total economical failure (several times), it worked quite well. It was even harsher in Ryzom.

Spells (or any action, for that matter) need to be balanced with a "counterweight". That's usually mana for magic and stamina for melee. However, unless you use spells that are way below your level, you do not have enough counterweights in mana alone to cast a spell (and you cannot possibly cast the highest spells even at maximum level). You have the choice to put in "time" as counterweight, or "hp".

"Time" means your spells take a lot longer, and during cast time you will be hit automatically by all but the lowest creatures and your spell fails. In other words, you're dead. So "hp" is the only working solution. Which means, of course, you can fire the biggest badass spells, but you are also much easier to kill.

It's certainly a risk tradeoff, but it isn't necessarily creating frustration, it may very well add to challenge (and very strongly encourages team playing).

As for the setting, a fantasy universe with godlike beings who have sufficiently advanced tech is a great idea, but how would you get across to the players that it isn't magical to them?

It goes with the story. Throughout history humans have labeled technologies they could not understand as magic.

Being a post apocalyptic story with dimwit uneducated tribal-like humans running around under the foot of evil maniacal dragon overlords, they are simply to dumb to know its not magic.

Because of how they are used (and overused), mana and stamina are basically the exact same thing in today's games.

Also, if you allow casters to use melee, then you'd end up where the only viable option is to use up your mana first and then your stamina so every player would always build casting warriors.

If you only have 1 pool, then you may cast or you may melee, or you may divide it, but you can't have both.

It sounds like stamina is a being used like an action point system. It fuels magic, melee, ranged, etc. Is there a mechanism for converting the health into stamina or does it just work on a 1-to-1 basis?

Stamina will be regained through food and rest (more quickly than).

Health will be regained through medicine and rest.

A drug could exist for those who have the skill to use it to sap health for stamina.

How original, a game where a class exist that takes drugs.

BTW, is this an RTS or a RPG or more of a TPS/FPS ??

I presume RPG/TPS.

Anyway, I believe it can be done.

Think of Blood Magic in Dragon Age, for example. In many MMORPGs, Necromancer also can do something similar.

The hardest part is to balance it out. You don't want players to keep killing themselves trying to kill enemies.