Hmmm...I assumed the damage dropoff for Keshik damage to cities in Gods and Kings was greater than or equal to the dropoff in vanilla.
By the time I hit the Industrial era in vanilla, my Keshiks rarely do more than one damage/attack, but I can usually bring a lot of Keshiks to bear in a single turn by that point.
That's been my experience when playing as Mongolia, but I haven't played many games with Mongolia that require trans oceanic amphibious assaults, which imply games that have yet to be decided in the late Renaissance/early Industrial Age.
I didn't want to have Navigation handicapping my progress.
It's good to hear that proper use of Keshiks can decide a game even on Continents maps.
Edit: I also forgot to mention the Knight buff in Gods and Kings. In vanilla, Keshiks had 2 more movement points than the unit they replace. In Gods and Kings, they only have 1 more movement point.