[Shovah32]

You said you researched destruction? With it cast on the vans they should be alot more vunerable to your arrows. I know its probably quite far away but if you can research up to magma eruption those vans should drop like flies. Your sacred statues should take very little damage from the spell(cast by golem crafters with summon earthpower) and with its high damage and AoE it should devastate those vans(with or without destruction). Umbrals should be very effective due to their ethereality(as the vans lack F9) and high health and could provide a very good shield for your archers after you cast destruction(again due to high health and ethereality).
A marble oracle with a shadow brand, charcoal shield and some other protective items(lucky pendant would be good. A ring of tamed lightning would be great if at-all possible) should also be able to hold out almost indefinitely against E9N4 vans(0 enc and with blacksteel full-plate should have around 30 protection).

There are probably about a number of other ways but those are just some suggestions, hope they help.

ps: I too hate it when i waste alot of money(bought a load of tribal indy archers and had to fight MA Ulmish knights...).