I went through this when I set up my touring bike using a MTB FD and brifters. I tried four or five different FD's (some road, some MTB) and had no luck. Either I could get a road FD to 'semi-work', or get a MTB FD to 'kinda' work! I guess it has to do with different amounts of cable pull. I could get a road FD to go from small chain ring to middle ring, but not quite to the big ring. I could get a MTB FD to do almost the same, but ran out of pull.
I finally gave up trying to use brifters, and got a set of DA bar end shifters. I wish I had done it a lot sooner--they work wonderfully! The front shifter is friction, and takes the FD (XT currently) easily from small ring through middle to big ring, with no problem whatsoever. I have the rear shifter set for index, and it works perfectly with my XTR long cage RD and 11-34 9spd cassette.
I did have to get a set of separate brake levers, and got Tektro 200's, which work every bit as well as the DA 7700 brifters I removed.
Now I'm considering the possibility of using a Mountain Tamer Quad, and wondering if the bar ends will cover four rings?