High level spell spam is a problem (if you can call it that) that can be addressed by mechanisms that are not implemented yet in the alpha (likely preparation time and presumably level requirements). In the beta, or at least release, the characters are probably not going to start off at level 1 with some of the most powerful spells/skills.
Reagents kind of limit experimentation with mixing various spells and seeing what tactics you can come up with. I'm all for being able to find item combinations and make potions, etc, but spell reagents would make that mandatory rather than optional. There were a few gameplay videos during the kickstarter where people were running around looking for mana potions, since resting, etc, had not been implemented; reagents could add that same 'fun' for everyone when they get to a tough fight that they need their more powerful spells/skills to be able to handle.
Other than being an inventory management 'make work project', reagents also add an element of luck to combat (if you happen to find or buy a few extra rare reagents, or not), rather than tactics.
