Cast the Verdant miracle on your storehouse. It beefs up all resources currently in stock, so make sure you've got a little of each to keep your bases covered. I believe it works worst with Ore, but you should still get something out of it :: .
It's so simple ......... Just don't waste ore on war.
A fairly short wall stood back from your TC is all you need a platoon of archers on it, for the early attacks.
.
Verdant is my favourite spell it "neutralises more enemy" than the "Lightning an kill" for a similar cost.
Your right it is life miracle which makes the ore max out. Anyway i won that land without armies. But ore shouldn't be a problem if you have the life miracle.
OK assuming you still want ore. 6 miners created at the start of the level should see you through to the end, they will mine other mines I usually rely on the ore from migrations.