| Reverend Keaton |
I will point out that Gasseous form provides no protection from the fire. A torch or bonfire is going to do a 1d4 or 1d6 per round. A fully engulfed building should do at least 2d6 per round. Vampires aren't required to breathe so they shouldn't suffocate but still being in a burning building would be traumatic for the vampire.
Also our lone vampire should be aware that there are hunters out there. Vampires aren't known for their loyalty either. I'd have the vampire save the most important members of the group and abandon the rest. Important being the master, plus anyone that the master will be really upset if they are gone, plus anyone they personally like (and can't just replace). Other thralls are just competition anyways. And the hunters will be less suspicious if they find a lot of burnt coffins. Ah, so many noble sacrifices. yep yep, no ulterior motive to this. Not like eliminating the competition makes the survivor look better. Not at all. And it wasn't just a regular fire. They used fire elementals too and that is why our heroic vampire thrall had to save the important people and leave the rest. yep. Only looking out for master!
Well the lone vampire was not exactly a real go getter when it came to helping others. He was a hired mercenary who was extremely good at what he did but could really if the rest of the party made it. He was a rather large d%$**ead and that was the way I played him. Booze, gold and good fight is what he wants. One of the party in a fight just prior to the one he died in popped out during a fight and went missing. He told the rest of the party if they wanted to go look for her they could but he was going to bed. So he was more of a save my own ass kind of guy.
I don't think the DM is really taking into account the character's lack of concern for his companions and his desire of self preservation. The next session may see where we end up with the fallout from destroying this nest.