[MaxWilson]

I'm guessing your problem is that your mages die to the generic, built-in missile weapons? Two things I can think of:

1.) If there's not a large army inside the fort, leave the mages out of the fight. It may or may not be useful to storm the fort with a single scout on the turn ahead of the main assault.

2.) Bodyguards help protect mages against missile weapons. With 3 units in the square instead of 1, you have 1/3 the likelihood of being the target even though you have a greater chance of losing the missile check opposed roll.

I assume you're already doing things like spreading mages out.

-Max