So I made an account just to ask this, I have a potato, but it runs Grim Dawn reasonably well(for my standards which are admittedly low) I never did crucible or shattered realm but I did farm for the dark one set in ultimate in that hidden realm zone where you face Lokkarr and after the first boss there is an area where things get really hairy and I experienced the lowest fps I had by far of any other area up until then, now it was still playable for me,but if it got worse then that in lets say crucible or high sr shards, I do not believe i’d be able to enjoy the game by this point.
Anyway blog post aside, that is what I consider a stress test of grim dawn, what I would like to know is if with FoA there will be an increase in system requirements, areas where things get as busy as in that hidden realm regarding the number of enemies present on screen/number of effects used or will it be in line with FG areas or high shattered realm levels (which I would also would like to know if they get as busy or busier then the realm where you face Lokarr/farm the dark one set)
Welcome to the forum. 
I don’t think much will change, if any, since Crate have said several times that they need to continue to support older systems with the game.
oooooh a moderator answer gives it the utmost legitimacy, I am very pleased to hear that, maybe then some other player can answer, if high sr shards get as busy as the area in Sanctum of the Chose before the 3rd Rift claimed Adherent?
They can, some of the levels have enough enemies and environmental effects that it gets pretty crazy. I think that messing with core affinity in task manager has helped smooth things out a little for me, but I am on a newer setup.
No idea about what is planned for Fangs of Asterkarn areas but I doubt anything will ever be as monster-dense as Malmouth.