Don't take this the wrong way Finian but your post made me feel a bit better.
You see I bid on a rather nice looking Dunhill Dublin estate that was at $20 with a few days to go on the auction, leaving a high bid of $105.
When I checked the next day it was over $300.
Reading your post reminded me that it's just a pipe with a fancy name. I don't really need a Dunhill because apart from the white dot, they're really no different to other well crafted briars.
Now I'm content to smoke my not so fancy pipes in my rotation which are all very good smokers.
Moisture could be an issue but if your baccy smokes fine in your other pipes then that would indicate that the pipe is the problem.
If that is the case then I'd be looking at the draught hole which might be too small, restricting air flow.
If you bought it as an estate the draught hole might have some hardened gunk that needs cleaning out [soak with isopropyl or grain alcohol overnight then clean it out]