I'm a little less than halfway thru a Kahdi marathon game. Turn 690 or so...
This civ needs some help imo, at least so far.
No I haven't popped the Kahd yet, and am going to pretty soon (have all the mana for the Tower of Divination and will use the free tech to get Strength of Will).
So far though, they seem very underpowered.
a) Intolerant isn't working properly in terms of stopping passive religion spread. As a result, I have a few cities with AV and OO, even though I have no open borders with the civs around me who follow those religions. I guess this is a bug, but not being able to train a unit with Inquisitor is kind of annoying
Another side effect of Intolerant is the same thing that handicaps Council of Esus civs. No healing, no disease curing. I have built both the Aquea Sucellus and the Shrine of Sirona, so that helps a bit...but it's really not enough.
I'm going to assume since I haven't seen one yet that none of the elementals coming through my gates are going to be a disciple equivalent and have medic abilties..so why not give Goslings the Medic 1 promotion. This would go a long way towards making them more useful.
b) No hero is a pretty huge handicap. I don't know exactly how strong Kahd will be since I haven't popped him yet, but even so it takes quite awhile to get to him and in the meantime, the lack of a hero unit is pretty terrible. Most civs get at least 2 heros, their civ hero and a religion hero (or several).
I'd love to see some sort of early to mid range hero for the Kahdi. Maybe attached to Knowledge of the Ether, or one of the 4 mana techs. An Elemental attached to Elementalism for instance. Str 6 perhaps, with the hero promotion, and maybe a +1 affinity to an element so that it can grow in power a bit too as the game goes on.
I do like the fact that I can currently make a mage in 2 turns...I popped a Great Commander from a lair, and adding him to the city where I built Form of the Titan, they are popping with 6xp, which is enough to get them to level 4 right away, and the next turn, I have a mage. It's nice, but even with the great equalizer that fireballs are, it's not making up the power difference.
Edit: 1 more suggestion...it seems the mechanic is there for this, though of course I have no idea if the in game mechanics are the same, but it would be nice if the Scions Awakened spawn rate % window could be used for the Kahdi, and show the spawn rate % for the elementals that pop out of their gates.
I'll post again later with some more updates and thoughts.