It’s pretty solid so far, I’d say Chrono 3, it just ages much better compared to flat bonuses Thaumaturge provides. Comparing both utility-wise, Chrono still comes up on top with Haste, Stop and Pass.
Thaumaturge directly gives defense in C2 though, and INT in C3, and Reversi has some uses in PVP. But infinitely more appealing and welcome in groups are Chronomancers, they are the only class you actually see called for in shout chat in the mage category.
So I’d say your next three circles after Thaumaturge C1 should all be in Chronomancer, if you stop at C2 Chrono cause of C2 Thaumaturge, you give up on Pass which is an amazing, game breaking ability.