To be fair we never actually saw what happened in Doma. For all we know the Garlean rule was pretty okay and the revolution was lead by a Griffin like madman. Stormblood will be the first time we see Garlean rule in action.
Also while it is true that Yda probably won't just fire the wave cannon at everything for the lulz, if a community is wiped out or a sacred mountain blown up those who are affected, might not care.
Well yes, that's where we first saw it. Of course it showed up in the interdimensional rift. And we know that the rift basically flows between the various Final Fantasy settings.
http://finalfantasy.wikia.com/wiki/Omega_(enemy)
You need to slow down the video speed to see it, but when White Dalamud is being formed you can see the outline of legs wearing boots inside. There is obviously a humanoid figure inside.