I know it says Dublin, and I have to say that I think Browns Barn is just terrible, and that includes the restaurant upstairs.
The Waterside Bar in Clondalkin does nice Carvery food, though it can be quite hit and miss sometimes, depending on the Chef and the Bar food in the evening is quite good too.
If anyone is out Kildare way, the Ballymore Inn in Ballymore Eustace is excellent.