One, Hache said his army was a half-day's march out. That means they're outside range for everything other than magic, we don't have modern artillery and cannot shoot more than a couple miles. Edit; even with a dangerous amount of powder behind them and a specialty barrel, which is what the marksmen are using, but the artillery itself can only reach a mile.
Two, no, Gwolf did not replace most of our traps with steam machinery without telling anyone, effective as it is, and even if he had, we have a cistern.
Three, while you can begin fighting whenever, Fish seems to be under the impression that he can go from having a polite conversation to fighting a long-range mage's duel in a few seconds. Dude, you need to set up, past a hundred meters or so it stops being reflex magic and starts needing forethought.
Four, Hache has his own few problems. Where'd you get a bunch more magic users? I've said before, and I'll say again, this world has a distinct shortage of magic users, there aren't a bunch of village witches and the like around for you to conscript. About the only way you could get large numbers of them would be to hand out "The Secrets of Life and Death" to your living soldiers, which would leave them highly inexperienced and of merely dubious loyalty.
Also, player-created NPC magic users aren't going to be able to outclass a player very easily. They're a threat, of course, but players are going to be stronger in most cases. Net is still fucked if five or ten lesser ritual mages pull an all-out attack, but they have to find him first. He could equally kill them like that, but he also has to confirm their locations before doing so, and it's possible to hide yourself from one another outside visual range. Doing so also makes casting at long-range a bad idea, because you'd leave a power-trace straight through your only real defense, though you can cast within the "Shroud" to a target within the shroud without crippling it.