If you're using magnets (even rare earth) I would HIGHLY suggest doubling up on each side. aka use two magnets in the base stacked on each other, and two in the model. You'll get a much stronger bond at the contact point.
That said, I've done considerable modeling and wouldn't trust basing metal models with magnets. Perhaps the malifaux ones are light enough, but if there's too much weight the dancers are gonna be twisting and turning whenever you handle them. It'd definitely work with plastic, but I think the metal will be too heavy and they'll end up chipping.
Personally I plan on just buying extras... but good luck with the magnets! double them up, hopefully it'll be strong enough.