A vampire might be able to burn down a house or tear apart a tent, using magic, catapults or whatever. This would allow it to go around the 'rules' and step inside ruins. It would still require it to do that from the outside.
Dwelling as per dictionary:
a building or place of shelter to live in; place of residence; abode; home.
If it is a residence or home to someone then it is a dwelling. It's indeed quite restrictive if you consider a cave system to be home to a clan of goblins, which most of us would do. If a hobo lives in a carton box that counts as a dwelling as well.
Restrict the 'zone' considered to be a dwelling though. Just as human houses have private gardens, roads nearby, or a swimming pool those don't get considered part of the 'dwelling'. Just because merfolk live somewhere in the ocean or on the coast the whole ocean/coast won't be classified as their dwelling, only their shack, hut, coral cave or whatever. If they live in a small lake the whole lake might be classified as that though.
In case of a cave of goblins the situation is clear if it has only a single 'room' or a few in all of which goblin huts/homes exist, but if it is part of a large cavern system only consider the part they live in and clearly control as the dwelling, and only if the clan system is family based, which means if multiple goblin families are part of that society then different homes exist and not just a single 'dwelling'. Think of village boundaries as example: even if it has clear borders it doesn't mean all villagers share a single dwelling and it also has shared 'public' territory like roads or a park.
If one wishes to have a vampire be greatly restricted then simply expand the meaning of dwelling, if you wish it to have ingame effect then probably this is a good reason for vampires to hire underlings to work and act for him/her in problematic 'dwelling' territories. This is one of the cases (among many) where the GM has full control of definition, so you might wish to discuss specific situations to have a clear knowledge on what to expect from a vampire.