Are there any casters that can't hold their own in a fight? They might all have some nasty tricks they can pull in battle.
Most of the time we have seen a caster in direct combat, they have actually kicked serious butt, though one should note they've always had prep time so far as I can recall. A few that come to mind:
- Sizemore would have been a prime target during tBfGK but he didn't even take a single hit thanks to tunneling and the protection of his golems
- Same goes for Wanda, she only ran into trouble during that battle when she took to the air with less support, and was attacked by (basically) another caster
- Delphi shot down all those fliers over Goodminton
- Every time Olive gets into combat like ever
- Ace fights pretty darn well even without using magic
So if a caster anticipates that they will have to defend their city, then I expect many disciplines should be able to hold their own.
Let's not forget Jack with Stanley fighting Jillian and Transylvito troops (even in a crippled state he was awesome there) and also trying to use a Purple Dwagon at Spacerock (not so awesome in this one).
As mentioned, when a Caster has juice and is on his element can be pretty powerful. But let's not forget that they can also make silly mistakes when trying to do things in battle outside of their comfort zone. Even Wanda with all her battle experience made her share of mistakes when trying to lead the battle for Spacerock without a Warlord's advice (be it Parson or Ansom).