[thejeff]

Largely true for the early game.

But early game can end well before turn 50. Of course, you have to devote enough resources to hiring mages to research to get the more powerful magics that will change the balance.

Even in the relatively early game, the large scale troop buffing spells can make a big difference depending on your nation. Flame arrows is an obvious example.
Once you've got a decent gem income, again requiring mages, summoned troops can replace those stomping hordes.

The obvious early game exception is the heavy bless strategy. For some nations a handful of blessed troops can slaughter those hordes with minimal losses.