Liadri is nowhere near balanced.
If Liadri was unbalanced, then she would have so much health that only players with Ascended quality gear and the highest damage-dealing build possible would be able to kill her. She would be so difficult that even when you learn every nuance of the fight that you would still die due to things beyond your control, and you have to simply keep trying until the stars align and you squeak out a win.
But guess what? She’s not.
Liadri has been killed by every profession on a wide variety of builds and varying skill levels. The best players boast about how they kill her in 10 seconds with gambits, while others rejoice when their victory comes as the announcer counts down the last five seconds. Players that have done it and continue to practice can repeat the kill, which proves there is little luck involved with victory or defeat.
I’d also like to point out that this is an incredibly small amount of the content available in the game. Liadri’s existence does not prevent you from doing the other 99.97% of the content you have access to which you apparently have no issue with.