The MX250 was always kind of below the nVidia standards. Above basic Intel integrated graphics, but below actual gaming cards.
In terms of required - that’s what Blizzard will support. Often things run, not ideally, but they run, below that level.
What it sounds like is happening is that it may not be handing off from Intel to nVidia as the game starts. Are you on the latest release of drivers for Intel AND nVidia?
It’s not on the supported cards list, but you may be able to get it working. However, the game and customer support won’t be able to offer assistance figuring that out.