It makes me wonder just how much worse the Arachnarok's spiderlings got. Because they really were quite good. We'll have to see.
@Mecha#4. Spider riders are really good for the "chase down" bit of a battle. They can even sit around until that bit if needed. The movement debuff is probably just as strong as the -attack part of poison, and it lets other slowish orc cavalry and infantry have a shot at picking broken units apart as well. It's not the be-all-and-end-all, and having some wolves around is always worth it anyway, but spiders are really useful for O+G to have a unit or two of in most cases. It's sometimes hard to find a use for them, but when you do, that poison is like mini-gobbo magic that you can position wherever you want, regardless of winds. They might not even need a faster support unit to chase with either, which is their real advantage compared to infantry night goblins. Or it's just fun to annoy cavalry and flyers with. Just kind of sling some shots around or flank/rear charge cycle splat them into infantry. Not for the damage they do, but because it's annoying and deceptively powerful. Poison is surprisingly underrated, mainly because it's an extra combat modifier, and you stack 'em like hell wherever possible anyway. You've got to have a combat advantage already for it to be worth throwing a tissue-paper endurance unit into a combat though. It makes it faster, it should save some of your proper combat troops, but working out when it'll swing morale in their favour or yours from the casualties caused is an artform in itself. At worst they're a few extra units taken care of if you're winning (or at least a few extra entities gone from a unit or two when they rally if your infantry and spiders really can't chase them right then), or the ability to dick around a goon squad/cav unit group or other flyers for a bit, and at best they're portable on-call magic. Or they can magnanimously bother to appear from hiding half-way through a battle and save a unit of yours from pursuers, or execute one of the enemy's that's running away. They're worth a control key, each and every unit (so, like 2 keys max usually), no matter what you plan to do with them. A unit or two of spiders are nice. Hard to use well, but with potential effects all out of proportion to their combat value, endurance or even kill counts. Not even horrible vs VC, because it's a little extra damage mitigation and quicker crumbling sometimes. Or just to splat them against two/three blocks of zombies/skellies/GG/whatever to hold them up for a moment (putting spiders to a max-width setup to splat against multiple units from behind is a viable use for them). Oh, and the occasional "hidden necromancer" safety setup from VC is funny as hell if the spiders just happen to full-move-speed by him and notice him from their own hidden placements in the backfield.
Wolves are annoying because you can't really play tag with them easily, and they're so cheap and inconsequential that it probably isn't worth it. Spiders are annoying because they can play tag with you if they manage to poison your units, and it's still not worth it to go out of your way to stop them tagging something. If you do, you lose meat on your front line or fast/flying/ranged units as deciders, which is exactly what we orcs want. But spiders have a threat value due to poison effects, wolves kind of don't other than their speed (which reduces people's wish to threaten them). People often try and engage spiders, simply because they can. All out of proportion to what they're worth, and well before they'd be useful in a battle anyway. Which is usually a win for you. Not to say you shouldn't try and win the cav war, but sometimes even when you don't, it's still a win for you, simply because "spiders are slow fast-cav" and thus were engaged as such. For a far longer time than was appropriate compared to what's happening in "the real battles".