I think you're right, the location of the Vulcan wasn't great, it was in a bit of a "no man's land".
There was a new-build pub further on, just past the fire station, I think it was called "Rumpoles' or something very similar? Now THAT really was an odd place to decide to build a pub. I don't think it was ever anywhere near busy, not even on a Friday or Saturday night. Given that it was directly opposite Cardiff prison, I wonder how many inmates used to look out of their cell window and think to themselves...
"As soon as I'm released, that's going to be the first place I visit!"