It's all over thr place. Most of the classes are generic enough they'd fit wherever.

Barbarians were historically from around Mt. Arreat (on a different continent to what is in D4), though I guess some tribes might've moved elsewhere through the course of time (especially considering we can make barbs to be of different human races they had to be in different parts if the world to develop that way). Especially after the Worldstone explosion they were scattered to the winds. The most barbarian zone is unintuitively the Dry Steppes - the cannibals there are a tribe of savage barbarians.

Rogues could fit anywhere - they are just shady people, assassins, thieves, scoundrels... that kind of stuff. You have that kind everywhere. For me they thematically fit Fractured Peaks the most, as people living in the shadow of the Cathedral but that is just my class fantasy of them causing it. There is a city for peolple like this in Hawezar, lead by a certified scoundrel so that might fit as well. Then there are rogues from the Sisterhood we saw in D2, which is another flavor, more organized and different fantasy behind them. Thematically different from your generic rogue and if I remember correctly they are splinter faction of Amazons who have their homeland on Skovos Islands (?) somewhere south and I think separate from the main continents.

Necros are naturally spread through the world as well, to keep balance everywhere. I think they do have some kind of "central" but I don't know the lore on that tbh. Hawezar might have general necro vibes with the witches being centered around death and rot and stuff but it's closer to the D3 Witch Doctor probably. Necros treat death a little differently (at least in lore - I always felt there is a disconect between gameplay and lore as far as necros go).

Sorcs, again, could be all over. There are different mage clans and stuff and moat likely all regions have their flavor of sorcerers around. Historically I'd match them with Kehjistan, as that was one the greatest nation and was at one point ruled by Mage Clans.

Druids are probably the only obvious ones with Scotsglen, that ia their homeland. But, they also live in other places. The player character druid is from a druid enclave across the sea for example.