Powerful keywords aren’t inherently bad, but you do have to be careful with them. Make them too strong, and your only options become “Have cards with those keywords be overpowered,” and “Have cards with those keywords be underpowered.” Ranged would be my go-to example, with most ranged cards being so unimpactful the turn they come out and so fragile that they’re unplayable, because if Counterplay wasn’t cautious with their stats they’d be game-dominating units. Which I hear ranged units are in Gauntlet, due to the lack of removal, not that I play Gauntlet.
Frenzy, forcefield, celerity, rush and blast are also very powerful keywords, and most of the cards that make use of them are bad, or simply not good enough, with a few of them being really good. I can think of one particular card that uses two of those words together and is seen in almost every deck its faction builds at higher levels.
Were it left to me, I’d change all of the so-far mentioned abilities, plus flying, to be less inherently powerful, and then see about buffing the individual cards that use them, as appropriate. If anyone’s curious to hear, I’ll happily tell what those changes would be, so that you may render your collective judgement.