Future of Boss fight designs

Recently played against one of the latest boss and it was such a terrible experience giving war flashbacks of Napuatzi (possibly even worse)

I'm talking about Lythara.

Its a gameplay nightmare of positioning that inevitably checkmates you to death. Attacks (persistently) taking up 40% up to 90-95% of the arena (spells also being so big it cuts you off from the other parts of the area) leaves almost nothing for combat especially considering the restrictive and underwhelming defense mechanics. I was lucky enough to be playing with AOE range spells. I cannot imagine how difficult it would be for melee builds. The fight seemed impossible after multiple tries and only learning later of the wisp gathering mechanic of the boss after I gritted beating it. Its an interesting mechanic but I believe it gives a false sense of skill as the arena is TOO SMALL that moving to the other area inevitably allows her to power up and acquire more wisps.

I imagine it would be better if it was a bigger open arena where positioning is an agency of the player and not solely by the boss. The mechanic then truly becomes about player skill being careful not to lead the boss into the wisps and not the boss just cornering you to your death. That 'restrictive zoning' mechanic works as a phase like in Arbiter and other bosses but its terrible as a constant & cumulative mechanic that just limits player actions. It gets especially worse considering this is a mid-game boss and not even a pinnacle boss where extra skill and preparation is expected.

If you want to include this level of gameplay then I suggest you have it as an endgame boss category. Perhaps the campaign version has a dialed down difficulty level with less attacks or smaller damage areas then theres a mapping or repeatable version of the boss with maybe this tighter arena and all these cumulative attacks and spells. Limit the damage sources on the arena to at most maybe 50% and leave the 90% versions to the endgame pros. I think there's little to no room for extra difficult gameplay mid-game when players are still trying to build or find their build (and especially how some only get 'online' later into the game)

P.S. it would also be nice to have replayable campaign bosses scaled for late game with possibly added mechanics.