Just killed Jelly King, group played really well - everyone brought the right weapons, was smart about vial use. We had exactly one death, and he didn't even revive before the King fell.
We only get 3 tokens? I felt like a performance like that at least deserved the elusive Fourth Token.
I'd love it if you were graded on your performance against the boss, such as by time, number of deaths, or energy revives. Keep the default number of tokens at 3, but let us earn those 4th and even 5th tokens by showing our best talents.
And to offset potential problems with elitists kicking players who don't meet the requirements, also make a metric to evaluate the quality of player equipment. A 3* only team that takes on Jelly King deserves at least a 4th token.
This way the game can further push the skill-based progression.
I don't know if this would encourage the right kind of play. As you stated, experienced players would boot inexperienced players out to get more tokens. This isn't even a matter of being elitist, it's simply practical. I like the current state of things where people are generally laid back about you dying a bunch, since it doesn't really affect them, or even benefits them if they revive you. And since loot is duplicated instead of divided, you can't really have anyone "leeching" off of your efforts. People seem generally content to just know they didn't die as much, and are rewarded for their skill by paying less energy and/or getting more heat. I'd be very wary about upsetting this as it's frankly one of my favorite things about this game.
Giving more reward while wearing lower tier gear might be interesting, encouraging higher geared players to "step down" to a gear level more appropriate to the encounter, making it a more challenging fight. It would also encourage people to build up specific equipment setups for each boss, since with lower level gear you need every advantage. Unfortunately it's unlikely such a system would be implemented, just because it's very counter-intuitive and feel like you're being punished for having higher level gear, instead of being rewarded for the time and effort you put into getting it.