Actually, I was thinking you could go past level 21 with a reformed HP formula, so that you have more HP to begin with, equal HP on level 21 and then gain less HP per level than you would now - so you don't get huge HP but you get access to more perks.
However I would want there to be more desirable perks than you have slots for - it should be a tough descision and you must always regret not being able to take something.
An extra +1 BRD is a choice - don't like it, take something else - other BRD would be exaclty like now so you lose nothing

Insta kills have been the same leve for a very long time (2 wipes now?) - anything changing is purely you thinking it.
Avv, if classes are that countering (they wouldnt be) then it would be a matter of mixing your team properly - in a similar way a loner must mix their char.
Rascal, not sure where you are getting any range changes from - only thing I'm thinking of changing is Plasma and Xl70 ... both of those increasing.