Eh the Zhonya's thing is expected. It works the same way as Vlad's pool, Elise's jump, or Fizz's hop. Darius rises into the air, but never connects with it, so the cd never gets checked if the hero died or not. It works the same way as Skarner's ult does, there is a windup before the move actually connects, and if you disjoint Skarner's ult it doesn't go on CD either. It seems inconsistent with other spells in the game (i.e. Taric's dazzle or Sion's stun which do go on CD right after cast, not on connection), but those tend to be ranged skills rather than a bit closer like Skarner and Darius. I believe Singed's flip works the same way, the displacement must occur for the CD to start (it has an extremely short windup).
Although I do notice that if you cc Darius during his wind up, it still follows through, akin to Ezreal's and Lux's ult. Not sure if intended or not, although Riot has mentioned that Ez/Lux's ults were meant to function like that.
In regards to the altars, it's not just Darius that is a problem, it's all bruisers. Altars require a champion to be on it for it to be contested, so squishy champions simply cannot do anything about it other than poke away and sadly watch the altar be locked for 90 seconds. Maybe a dominion style counter would be prudent. Champions that stay on the altar start capturing it, damage source stops them for countering for a very short period. This allows ranged champions to actually have some influence over captures and leads to more dynamic altar engages, rather than simply take the beating and scram afterwards.
I also found it confusing that in a map with no wards, a speed shrine was also placed. Yes this makes ganks fast and furious, but it leads to scared play, where you don't venture too far from your tower in fear of being ganked. I agree that wards should be removed in such a small map (requires almost no gold investment to be safe from ganks for both lanes), but a speed shrine tips it over a little. Maybe have the shrine ramp up speed as you stand on it and decrease when you leave it? Or simply have a decaying speed buff when you move off it.
Overall TT feels much better in that jungle isn't reduced to essentially Nunu, Lee, and Shyv (although they are still godly), ganks are easier to come by, and pushing isn't punished by turtling. It's just frustrating that bruisers control most of the action (although being balanced around 5v5 does make it a problem for 3v3s i.e. Olaf only having to deal with 3 sources of incoming damage rather than 5), and altars don't help this issue.
Thanks Nome for your time, I was a fan of Nome's Wisdom back in HoN haha.