I'm pretty sure that they were dead in that split second when the bomb exploded and that the deaths were painless and instant. And the bodies were all for a short period of time Crystallized by the power of the explosion along with most material things though it seems not everything was Crystallized seeing as the horde were sent in to loot Theramore shortly afterwards. Won't go into details cause I'd have to rip the book out and look over the explosion again cause I'm not 100% sure on every detail.
As for the Scenario I was disappointed in both terms of how they thought that the Theramore Scenario would be the most logic way to introduce Scenarios to the Community at large and in the in scopes of the last two Events before the launch of previous Expansions I'd say I'm extremely disappointed in regards that it didn't have a little more to spice it up, something simple like the NPC's in Stormwind mourning the loss of so many lives and the importance of those particular lives and the Orc's in Orgimmar in festivities or something and some NPC dialogue to express there feelings on certain points within the book so that people had some type of grasp of what had gone on before the Scenario. Least that would have made up for the appalling overall feel of how bad that Scenario was when compared to the others I played on the Beta.
And thinking on it, there was really alot missing from how they could have told the story with Theramore <for both sides> when compared to other scenarios and with how Blizzard wishes to convey new aspects of Lore and Story Telling to the Community seeing that they have done a extremely awesome job of that in MoP and I hope it only gets better in future expansions.