I'm not sure which of the fights OP is talking about. Final stretch of the game is basically (size as in number and toughness of enemies)
1) large fight ->
2) get to next fight ->
3) medium fight & small final fight

I only did it once on default difficulty and did it as good-aligned. I used plenty of allies in the first fight. I feel like the first fight was really bloated but the difficulty was non-existent with all the allies provided. One or two ally deaths and pretty much no resources spent.

I expected something rougher for the second fight. Used the AoE allies that was one-time use and nothing else. Wiped the board clean before entering the area for the final part of the fight.

I get that this kind of game can be really hard if you don't put some thought into builds and equipment used but if anything I'd like the first part of the fight to be a bit less bloated and a bit more spread out (everything bar 1 or 2 enemies got pulled into the fight). I believe the final parts are fine due to the time contraints but I only spent a fraction of my renewable resources to get through it. Compared to going in blind for the "Halsin fight"
lift curse
it was too easy if anything.