I think the big problem going on here is that too many people assume they knew it was going to fall. You ask me, the whole MoT thing should have taken everyone by surprise. They knew it was going to fall, so they tried to stop it. However, the machine blew up, and it crashed. To most, if not everyone, they wouldn't know when it did till it actually happened. In addition, the eruption of Red Mountain would have ruined many modes of transportation, and chances of survival, since it was all so sudden.
Frankly, only very few people could have escaped, and I highly doubt even the most powerful or resourceful of the Telvanni could even escape it. People here seem to forget that a lot of the Telvanni are a bunch of oldies stuck in their towers, hardly ever looking outside, completely consumed in their research.
I'd agree with this. I doubt Vuhon and Sul were even telling their fellow Dunmer how the Ingenium worked; I think a lot of Dunmer would have been angered by a machine that required souls in order to run. Most of the ordinary Dunmer would have died like flies when disaster struck, without access to teleportation or levitation, or even access to ships without being swamped. A few nobles and adventurers might have been able to figure out what was happening, but I bet casualties were high even for them. Probably the only areas able to ride out the tsunamis and pyroclastic flow were those coastal areas, including Sheogorad in the north, that happened to be farthest away from impact.
http://en.wikipedia.org/wiki/Pyroclastic_flow
Interesting quote from that:
"Testimonial evidence from the 1883 eruption of Krakatoa . . . supported by experimental evidence, shows that pyroclastic flows can cross significant bodies of water. One flow reached the Sumatran coast as much as 48 km (30 mi) away."(Not that I'm an authority or anything -- only found the article above.)