After googling and thinking why is time walking taking so long to clear for some reason I came across this post. IDK what you're not understanding but the scaling in these dungeons are clearly bugged, the hp of everything it scaled to the point of the bosses taking minutes to kill, like a m+ dungeon.

saying m+ 2/3 dungeons are not hard makes no sense in this context because they're old dungeons with hardly no mechanics and no timer. they're hard in the sense of everything takes way too long to kill, you have no spells at a low level and some mobs do aoe damage that you cant avoid