Want some more? Here is my "I wonder if they tried everything" anti-Helheim list. It keeps growing every day.
So far the best thing seems to be investing all of one days gold into PD on some important chokepoint. Of course that doesnt help the small-map blitzers.
Aim boosting spells and Bow of War? (volley of arrows, area affect?)
Awaken Sleeper for a strong commander, give him Thunder Bow (that uses strength boost) and Eye of Void (to see thru glamour). Does giving that Eye of Aiming make him blind or would he still be able to shoot? He has pretty good precision. Adding strength boosters would speed up the kill with that bow.
Do spells like Eagle Eyes help?
What about attacking equipment like the dancing trident or that dove?
Slingers broken up into many small units.
Snake Bladder Stick
Hydras
equipment: Wall Shaker
elementals seem to do well
Spirits of the Wood? Watcher?