Don't the abominations and juggernauts seriously lack slottage? Otherwise they'd be great! The same with Tarrasques, although Nature gems are precious.
The gargoyles are also lifeless, which is a great bonus if life-drain weapons are available... On the other hand I've fitted the Monolith armor on one three times already only to realize that no, it won't regenerate
They do require rare mages to make (or maybe that's only a twisted perception based on what nations I've played), but I guess Vanheim would have no trouble if druids are to be found.
I wonder where I copied the idea... Must have been the SC competition a while back.