I remember playing reboot and trying to main DA, early game bosses like chaos crimson queen felt really good to figth against because she did flat damage, making DA maybe the only class that could tank her attacks while dealing meaningful damage in return.
My brother and i used to play reboot, me as a DA and my brother as a shadower, besides the Chaos crimson queen fight, i felt like burden in every boss fight because most bosses deal % damage, making the supossed tankiest class just weak by not being able to heal nor burst, i can definetly relate to your post, i felt like DA on paper makes sense but in practice its a diferent story. i ended up quiting reboot and starting over on bera as a cannoneer.
The thing with Demonic frenzy, maybe they could give it a 2nd stage cast, like thief's last resort, that fixes your HP to an optimal "burst range" by a set time or something.
the amount of ppl quiting DA its just sad, give this class some love like you did to illium nexon.