Well, Bull mentions that they have Dwarven ruins in Par Vollen, and I'd say there's probably a good number of Dwarves who may have gone topside over there when they were cut off (from perhaps cave-ins, sacrifices, etc.), settled on the surface, and were eventually taken into the Qun. Throw in converts and they've probably got enough people to work with it.
Granted, they would have to live under the laws of the Qun, meaning that even though they provide something valuable if they're better at cooking then whoops there's not going to be any lyrium-reinforced ships, military advantage be damned.
Still, given that Bull says Dwarven ruins are over there, I'm gonna labor under the impression that there is a sizable quantity of Dwarven Viddathari, but they're certainly outnumbered by the Qunari.
Even so, without official lore to go with it, I'm just drawing up a bit of headcanon here. Alas, it would be nice to know if they use lyrium. I recall the Qunari woman in the comics used something that seemed to be like lyrium, if only in effect to others and how it rendered them akin to Tranquil.