More or less. Just depends. Since the cost of the Harab Elder is so high, you couldn't be building much in the way of both Gryphons and Harab Elders.

You would have to rely on Storm Guards/Raven Guards + Gryphons in order to compete. The slower movement of the Gryphon wouldn't allow it quite the movement of most of Caelum troops (Letting them jump *everywhere*).

It would also force the smart use of Storm. You don't have nearly the battle power as base Caelum, since you don't have Quickness with your Orb Lighting, but lets you have a chance to get a 3rd Death (for say Terror) or a second Earth to be able to forge Earth Boots then Dwarven Hammer (something that Base Caelum has no chance for).

It is hard to fill the gap of the mammoths, as they are an incredible unit and very cost effective for use against indies and high amounts of elite units from opponents.

I'd have to be tested, but it certainly would make you think differently from base Caelum, but have the options where it is not considered 'totally useless'.