I'm not terribly concerned about the recommended specs because the top-down view that gets used for this sort of ARPG just naturally tends to perform better than, say, an open 3D world from the 1st person perspective. A top-down game doesn't have large draw distances. Lighting calculations can be simplified somewhat, too. It's easy for the game engine to tell which objects in the level are in the potentially visible set; no occlusion to worry about, etc...
If anything is problematic it's probably having a large number of monsters on the screen, but again, with a top-down view the game designers probably have more control over that factor, and you can also optimize your monster models a bit better when you know they're always going to be viewed from the same perspective.