Quote Originally Posted by Kurald Galain View Post
The key here is "every enemy".

It's fine if some enemies you meet are resistant to your strength, or specifically attack your weakness. It's not fine if all of them do. For example, I once had a wizard character who was fond of the spell Flaming Sphere (which, I should note, is nowhere near overpowered in the first place). The DM decided at some point that a large enemy could use his club to hit the sphere and make it fly far away like a golf ball. Now it's fine and funny if that happens once... but from that point forward, every single time I used the spell, some enemy would kick or punch it out of the combat area, making the spell completely worthless for the rest of the campaign.

Don't challenge PCs by negating their strengths. Challenge them by attacking their weak points.
When the strength of the PC is "has no obvious weak points" that's rather difficult. Im not sure how "Only faces enemies that cast spells that allow for no saving throws" is any less contrived or annoying than "Only faces enemies actually capable of striking you in combat".