I've found this question and answer on Facebook page of Heroes.
Q: Creatures buildings (dwellings) will be specific to each creature or will there be a building per category (core, elite, champion)?
A: There will be a building per category.
If I understood this correctly there will be only 3 buildings from which you can hire all 7 types of creatures - so I guess when you build core tier building you will be able to hire 2 or 3 different creatures. This will speed up game significantly and I can't decide if this is good or bad thing. Does this mean that there will be much less buildings to make in towns? What do you think people?