Against Hard AI
I think I'm a halfway decent DG player. I'm not too daft, I understand the mechanics and I developed my share of strategies and adapted some from those that know better.
So I should be able to win against hard AI, right ?
But no matter what I try, these bastards are hard to kill. And even when everything goes in my favor - flags, duels, creeping - they inevitably pull ahead of me and gain levels fast than I do.
Consequently, they start to wipe the floor with carcass, especially since they tend to gank me.
So eventually I thought "fuck it" and maneuvered around them, picking fights only when necessary or in my favor. I trashed their base defenses which do not benefit from the hard setting and munched my way into their base, nearly unopposed. An allied AI even caught on and followed me in, enabling us to capture a portal, trash more defenses ... and even their citadel, while most of their DGs wandered around ...
Looks like they neglected building upgrades and the 24k hitpoint citadel was dust pretty fast.
And in the end we - the underdogs - won.

I'm the sucker called Aroddo, with barely 8 levels against Torch Bearers 14. And yet that was enough for me to tilt the game in our favor.
So, the lesson learned: If you can't beat them with power, beat them with strategy.
Oh, and I used this build: http://demigod.wikia.com/wiki/Demolition_Man_Rook_(Guide)