[Squirrelloid]

Ok, admittedly SP, but here's my results with E9 plus some assorted other things (F4S4)

Independents:
As few as 3 spiders routinely beat independents and never acquired either an affliction nor lost a rider.

Typical deployment was 10+ of the machakan spear infantry (no armor, shields) front and center set to hold and attack with spiders (usually 5+) on the side set to attack rear, often leading to the spiders intercepting advancing meleers on the side (breaking up their formation, but generally resulting in at least one spider being swarmed). The good protection helped avoid injuries, but also webbing prevented numerous troops from attacking.

(Archers were used as appropriate against suitable indie types like barbs, although just 3 spiders generally did just fine against tribals or standard (militia/light/heavy infantry + archers) independents in not unreasonable numbers.)

Against AI:
AI armies were slightly more worrying, actually succeeding in occasionally killing a spider or two. Some afflictions resulted, although most of them weren't relevant. (Never Healing Wounds and Weakened are mostly irrelevant, for example. Never saw a crippled or limp black hunter, which would have been the most annoying. The worst affliction i got was diseased, and when the rider died the spider was not diseased iirc).