The sheep bonus is awesome, lets you delay farms until you research horse collar + insane amount of bonus wood/food early game (depends on where you put villagers). Way stronger than the house bonus assuming you won’t get housed.
I found free thumb ring much more valueable than -10% cost in castle age. The cost reduction bonus basicly means you get +1 cavalry archer for every 9 which isn’t that big.
Much better lategame cavalry archers (with +1/3 armor), and free parthian tactic comes in handy. When you’re in imperial age you most likely got enough cavalry archers anyways that the -20% cost reduction doesn’t count much.
Tatars have FU camels which are insane versus cavalry, huns rather have stronger knight line (I prefer camels).
Hill bonus is awesome.
I think +2trebs are better than trebs with more accuracy.
Buffed flaming camel, who knows if it will be viable after the patch.
I found keshiks to be way more powerful in tarkans overall, you get a nearly as heavy tank as the paladin for basicly half the cost.
Huns are a way older civ with big reputations and cavalry archers are neither that popular amongst players these days I think this basicly explains the tatar winrate and playrate (rather than weakness)
Overall I’d go for a +10 gold cost for keshiks with higher gold generation rate change, but I think tatars are fine.