MT21s will be great for your intended use. They excel in Rally-type conditions on gravel. The rounded profile and flat knobs let them slide predictably and hook up.
An experienced friend runs them for our West Texas dual sport called in Terlingua and buys/mounts up these tires just for this event. He flat FLIES on these things.
I ran the MT21s before too and they do work great on gravel. Suckola in sand, OK in mud, great on the hard stuff. Pavement too.
BTW, I'll be going up the mountain in a few weeks on a KLR with 'stone ED01 front/Trail Wing rear. For a knobby these do well on pavement too.