[krpeters]

One thing I noticed: you didn't specify what difficulty AI you're facing. If you're up against Mighty or higher, and several AIs at once, you're going to be consistently outnumbered by his hordes. High PD (30+) will help you a lot. Keep your "real" troops and mages behind it, let it take the attrition while your major forces strike from the sides.

You also need lots of low-resource mobile forces to manoever flexibly and outnumber his troops wherever you meet. The standard Horseman (move 3, resource 13) you can mass large numbers of. They'll plink the spiders for a while, then when the spiders start chomping on them, they'll stomp back nicely (thanks CBM1.7 for giving them a Hoof attack!)

Magic-wise... you might get more out of your Imperial Geomancers. Pop a Light of the Northern Star (you'll need 5 in a communion, set last to Master), and then spam Paralyze. That should take down spiders nicely.