Ultimatum round 8-10 Rewards on t14-t16 is a joke.

Im done pretty of these just as random master.
There's no good rewards for high rounds at all.

No divines, no exalts, no exalts shards, no 21/20 gems, no enhance/enlighten/empower gems, no uber atziri fragment sets,no good synthesiced bases - there's absolutely nothing for spending like 3 min for each of these encounters.

From Rituals for example - i got so far:
1.Around 4 Divines.
2.Around 20-25 Mortal Ignorance (which is ~50c each)
3.Some 21 gems, some 23qual gems.
4.Lots of small usefull curency - orb of horizons/regrets/scourings, t14-t16 maps etc.
5.Enhance gem
6.Several good bases 83+ iLlvl6-links

I don't get how rewards in more simple and stable mechanic is 10x times better than in harder mechanic?

Without investment ultimatum doesn't give good rewards often aside from shitting out catalysts, that much is true. You pretty much have to take "Stand your Ground" (receive rewards as if a round higher) as well as the "Gruelling Gauntlet" keystone (+3 rounds, but no chance for boss) if your primary objective is getting Inscribed Ultimatums as well as rewards of your choice (use the Inscribed Ultimatum wheel to modify the reward types you receive most of).

Ritual is more of a generic loot pinata with solid rewards whereas Ultimatum lets you target certain rewards. I have had several multi Divine Orb drops as well as an Apothecary card from it. So good rewards are possible, but it's not a mechanic I recommend running vanilla

ultimatum is extremely unrewarding. i got 5 chaos once. that was my biggest reward to date.
i just wanted inscribed ultimatums so i can do the challenge but nope...looks like i will have to buy all 10 of them. (yes i took the points for it, didnt do anything)

Got few divines and plenty of catalysts, also some decent corrupted uniques. I also killed few trialmasters. Seems reasonably rewarding.