I've got Tiagra on a Cross Check. I bought the whole bike.
So I guess I only have the front and rear d-r's. They seem to work fine.
The crank that came on the bike was crap and made shifting the front a total crap shoot.
I changed it to a Dura Ace crank and no troubles.
The bar-con DA stifters work the way they are suppose to.

So if you think it's the d-railer that makes the shift, or the set up and cables; Yea it really works well.
If it's the shifters. I have no idea about Tiagra.