I imagine any cartoon would need to be profitable as its own entity. If it drives people to other Hasbro products, great.
If you want a kids show, a D&D cartoon ain't gonna drive kids to play, because D&D ain't a kids game. You could market to teens, but I don't get a sense that they watch too many cartoons. I don't know the demographics, though.
An adult show could appeal to nostalgic gamers, sort of the same way Venture Bros. appeals to nostalgia over old cartoons, but you've got less chance for secondary revenue like toys. Adult Swim is a cheaper market to air in than afternoon or morning kids cartoons. Spike and Sci-fi both are willing to air cartoons, but I don't have a friend working at either of those companies to give me vague statistics.
You could possibly do a web toon (the Adventures of Gnome and Minion?), but then you're getting even fewer viewers, and would basically be doing it just to drive visitors to your website.
I'm not really sure there's an on-air market for a D&D cartoon. Something like Venture Bros., while awesome and popular, costs like $250k an episode to animate.