There is the Wood Elf Sword that autowounds, and then does a 1d6 ld vs ld no saves of any sort for further wounds. That can take down a STANK fast. As can the Runefang. Honestly, the worst thing a steam tank faces is 20 skinks with blowpipes. Or any poisoned ranged attack with enough behind it. Sure the save is 1+, but make about 10 saves a round and it rapidly dies. As for Chaos, sure, you're limited on doing things about it. Flank charges with Knights is likely the best that you can expect.
Cant see the spirit sword working TBH- you have 4 attacks, which will all hit and wound, then the stank has a 2+ save to fail. SO you might do a wound. The you have 1D6+10, and he has 1D6+10 and whoever scores higher does that many wound to the opponent... with equal Ld you are just as likely to wound yourself as the enemy (and since you would need to do another 9 wounds to the enemy, vs the 3 he needs on you its unlikely you'll win). Although take a potion of strength and you'll be doing well. S7 means that the stank will have 4 5+ saves to make, and then is likely to be rolling for the spirit sword 3 times.. which is pretty likely to kill your highborn, but if you are taking a few more wounds off the tank you'll have ended its usefulness for the game.
I always think its the first 4 wounds on a steam tank that are the important ones. If you can cause 3-4 wounds on a stank then its usefulness will mostly be ended. Most of the people I play against dont risk more then a 1in3 chance of overpowering the stank... so if you do 3 wounds they'll normally only try for 3 steam points (or 2 steam points if you do 4W). So thats knocked the stank down to 2/5 or 3/5 effectiveness... plus then it'll start to rack up wounds on itself, fast becoming suicidal.
With the aim of doing a handful of wounds onto the stank most armies can combine auto-wound weapons with a potion of strength to charge in, cause lots of wounds and have a decent armour mod from the extra strength. If your lord is in a decent sized unit of chaff (cheapest stuff armound) then the reduced number of impact attacks shouldn't kill his unit too fast (and with his Ld he should stay there).. you are then forcing quite a few saves from teh tank each turn so should be taking about 1 wound a turn. So, do ~3 wounds when you charge.. then do 1 a turn and the steam tank should only really get 1 decent set of impact hits on you before its taken so many wounds as to need luck to get any steam points (at 5W its only 50-50 on managing to get 2 steam points... and 2D3 impact hits probably wont be enough to kill a rank).
As for chaos knights- NOOOOOooooo, keep them well clear of the steam tank. Marauders are the way to go for counter-units, preferably with great weapons and frenzy (ignore terror and extra attacks). Get into th flank and you can have upto 18 S5 attacks (could go 24 with hoard... but steadfast is more important). You should still only be doing 1W a turn... but get a little lucky and you'll take enough to start knackering its effectiveness (and if nothing else you have your cheapest unit holding it up)... you could then have a lord in there to try to up the damage or put in festus to reduce the damage you'll be taking.
3 ranks, banner and 1 wound a turn means that the stank would need an average of 3 steam points to draw... throw in festus and it'll take 5 to beat you, and losing 5-6 marauders a turn is next to nothing. ANy magic that makes the steam tank have a worse save (either -vs to it, or +vs strength to the marauders) will help.
Im not sure how poison works against WS0 enemies... the rules say all attacks hit automatically, but it doesnt say you dont roll to hit. So Im wondering if you would roll the 'to hit' dice, with them all automatically passing but with 6s being poisoned. Opinions?
