it doesn't overwrite the game. It's part of the game. The higher the level the more stuff available to deal with and the more stuff available for DM to use. Of course it gets harder because you have more things to keep in your head or to plan for. That's true if you take mages out of the game. If my high level rogue player is meddling in trade between 3 kingdoms with his current guild he's running then I have to deal with all the players in three kingdoms, decide who they are what their resources are and how they act.The argument was that spellcasting in D&D becomes a problem that requires special preparation to counter, or else it starts to overwrite the game. You disagree, and then list all the ways you can specially prepare to avoid spellcasting being a problem that overwrites the game.
You see this, right? It's not a matter of "oh, I can deal with that," it's a question of what it is you have to deal with and why.
I've played in games with DM's who love rogues so much that the rogue becomes the guy that makes everyone feel useless because they always know everything and nothing can happen without them. Anytime you as the DM let any player take that spot in the game you have failed to utilize your resources properly. I'm just disagreeing that it overwrites the game. I'm saying if it overwrites the game it's because the DM isn't utilizing all the tools properly. Mages are only disruptive if they always know what they are going to do and who they are going to fight. If they don't know what they are going to fight and you are mixing up things properly at least 50% of thier spells will be useless to them. there is no other class that I can so effectively screw by throwing a curve ball at them. I can turn 50% of any mages resources into useless anoying choices just by mixing up the monsters I throw at them.