Looking back on how I set up my older gravel road riding rigs, I usually opted for a set up with a 34T low gear in the cassette as a minimum, and in the 9 speed days, one could use Shimano STI levers and a big ol' Shimano long cage derailleur to get the job done. Then things got weirder with a lot of bicycle componentry. The story is long and sordid, so I won't get into that, but now with things going to eleven speed the older ways don't work quite so well anymore.
Take for instance my Raleigh Tamland Two, which runs the newer Ultegra 11 speed stuff. Even with a 32T low in the cassette, the front chain ring is a 36T on the small side, and that is no where near the low gear I needed on my GTDRI last July. Unfortunately, they haven't managed to get the XT level 11 speed stuff out there yet, but when it comes I will be slapping on a 11-36T cassette on that Tamland and then we'll be talking.
Fortunately, Gevenalle, (formerly Retroshift), has made their shifters available in a 10 speed version that works with a Shimano DynSys rear derailleur. That means that at least I can move some of the old 9 speed stuff out and get into 10 speed gear and keep the big gears going out back until the days of 10 speed come to an end. I've got my Vaya set up with an SLX clutch style rear derailleur with these shifters now and so far it has been great. I hope to get some good gravel road miles soon on this set up. Gotta get some fitness back after a January of doom.