[Truper]

I think the AI's reluctance to use "gems" if the target isn't very threatening may also have something to do with it. For instance, if you prepared for what you thought was going to be a big battle by scripting your mages to do heavy-duty casting like Wrathful Skies, but your opponent moved his army away and you end up facing a few province defense instead, the AI will override the Wrathful Skies order, and substitute something else that doesn't require gems. This behavior was implemented to stop what was a standard tactic back in Dom1, which was to Teleport or Trapeze a single mage on top of an enemy army, causing that army to follow its scripts and expend its gems, and thus be crippled when the main attack came during the movement phase.

Bottom line is I don't think the Wind Ride/Hellbind tactic can be made to work at all these days.