Question on Casting Dome Spells

[Teraswaerto]

Astral Dome is the best deal IMO, good % of stopping spells and not that expensive, and I always try to cast it at least on my home province + any other capitals I've captured.

[calmon]

But astral dome needs extra gems for every turn it should last so i would say its expensive in a long run. I'm to stingy to spend extra gems if not needed

[Aleph]

I think I've heard of people casting Dome of Corruption as a trap (on a narrow chokepoint - force your enemy to walk through the Dome to get to you). Besides that, I haven't heard of any other dome uses in MP.