I'd hazard a guess that most folks building a touring bike up from the frame don't use "group sets". I know I didn't on our 4 touring bikes that were built up from the frame. What I wanted could not be found in one group set.
One the most versatile set ups that I used on three bike, including my wife's custom built frame was: XT hubs, LX rear derailleur, Tiagra 4503 front derailleur, Sugino DX 500 44/32/22 crankset, Tiagra 4503 shifters(brifters), and either LX or XT 11-34 cassette. Using a mtn bike crankset required using a 103 mm length bottom bracket to get the 46 mm chainline needed to use STI shifters/brake levers. It is a 9 speed set up, which works very well. It is a combination of parts that over time I found work together very well.
The 44 high chainring with the 11 tooth rear cog will give you 28 mph at 90 RPM. I find this to be adequate for almost any touring situation I've encountered. I usually use down hills to rest, and do not need to peddle going downhill. I've never wished for a higher gear on a tour, but there have been times when I would have used a lower one.
This is my LHT that was built up from the frame.
