The Malazan Empire will have to be powerful in order to be faithful to the concept. It has, after all, conquered 2 continents, and was working on a third at the beginning of the Gardens of the Moon.
It should, IMO, be right up there with Pythium in relative strenght.
High mages are rare, and should be quite expensive and definately capital only. I'm pretty sure weapons can't be given area effects, so it isn't possible to model the Sappers accurately (yet).
If you include the Hounds of Shadow, they should be a lot tougher than Shade Beasts.