I don't think you should be judging khans based on your experiences with regular great generals. You're clicking 'do nothing' with regular great generals because (a) you don't use them to heal other units, and (b) you're most likely not using them alongside 5 movement units. But when it comes to khans the extra movement is very useful to get into position to heal in certain situations - otherwise you would have to waste a turn or two to get into position. Furthermore khans are very synergistic with keeping up with keshiks, and later supporting and healing upgraded cavalries that also have 5 movement (and march). Khans allow you to get to the battlefield sooner by many turns (without the need for roads). Considering that you can take down a city in 2-4 turns most of the time, when using regular great generals without roads connecting to the battlefield you'll almost be done with the battle by the time a great general arrives, but khans will be relevant starting from the very beginning of the battle and will be able to heal starting from turn 1 of the battle as well. Even if khans get 2-3 more turns of being in a battle than a regular great general, keep in mind that the rest of the battle may only last 1-3 more turns. All of the above are possible only because khans have increased mobility. The movement is crucial.
Lastly, khans have excellent synergy with late-game units as well. Immediately after keshiks, Mongolia will continue with uber-cavalries (which have 5 movement and retain the 50% experience bonus) and uber-landships that synergize perfectly with khans' 5 movement and healing bonus even moreso than khans' synergy with keshiks because (a) melee units take damage when attacking and therefore will benefit immensely more from khans' healing bonus, and (b) cavalries use hit-and-run type tactics and landships/tanks use rushing tactics which benefit immensely from being supported by 5 movement khans (rather than a stationary 2 movement great general).
In my opinion:
+2 points for mobility
+2 points for healing
+1 point for availability (can get one immediately with honor) and relevancy throughout the entire game, rather than being limited to a specific era as with most other unique units, while providing synergistic benefits to many units
Thanks for the nice response. My reply, in random order, and trying to stick to Consentient's thread theme:
+1 for mobility for my previous reasons. The mobility is great, but at some point I have to downgrade them for the fact that every warmonger game I play I end up with so many GG's hanging around I'm tempted to delete some to save on the GPT. If you have that many, mobility is an afterthought.
+1 for Healing. Maybe +1.5. My starting Warrior, almost every game, takes the healing promotion. From t20 onwards, that's worth a @$%^load of healing during the game. Is the Khan's healing THAT much more powerful? Sometimes, yes, but not always.
+1 for Availability. Maybe +1.5 so I can go down the right side of the Honor tree first. But that means we miss out on doubling up on the extra XP UA, yes? Perhaps I'm wrong in going down the right side of the tree, and I do love that 2nd level +1 happiness/culture. It's useful, and I find the 3rd level cheaper upgrade to be worth a fair sum as well, so i can see both sides of this argument.
As far as "Uber Cavalries" go, it is entirely possible that I misuse horse units, so I underrate them in post-industrial warfare (which is what we are discussing). They are also terrain dependent, to some degree. That said, I usually upgrade my Keshiks to get range and logistics ASAP and that means they don't always get Shield or March. At this point, upgrades, even with the double bonuses take awhile, so the "non-Uber Cavalries" do take awhile to become Uber again.
If we've done a great job with Keshiks, and there isn't much left to conquer, great. But if there is any real resistance and you don't have Arties/Bombers ready, you are kinda stuck in the mud at this point, no?
And since we've already focused our tech on certain military beelines, well.....we are now waiting around until we have a military advantage sometimes. Since our tech likely is slow right now, and the point of the thread is how each civ's military advantages contribute to ANY VC, I'd say that this is a weakness.
Since none of the above is remotely original, let me close by saying that I agree with those who have pointed out this weakness previously. I think Consentient has them ranked pretty accurately, but with the caveat that they are more terrain dependent than some other civs.