Offensive Rituals vs Summoning?

[TwoBits]

OK, I've played a good amount of SP games, and a handful of MP games, by now, and I've noticed that ritual attack spells (such as Fires from Afar, or Hurricane) seem to be a rare occurrence in both.

It just seems that most of the time, when you're engaged in a serious war with someone, summoning combat units seems to be a more effective (or at least more tangible) use of sparse gem resources, at least at early and mid research levels.

Granted, there are a few attack spells that seem very potent (like dropping Flames from the Sky on the big enemy army, or Black Death on the enemy capitol), but these generally require level 8-9 in the respective research category. It is a rare game that lasts long enough, and is hard fought enough, to truly justify the use of these hard hitting spells (I've never found them "necessary" yet).

So again, what am I missing?

What spells of this type, either to directly attack enemy units, or their population/economy, do people really find useful? Especially, what do you find more useful than summoned units that are able to contribute directly on the battlefield, and for a similar cost in gems?