It’s because enchanter1 has only enchant lightning and you need to put int to take advantage of it. In rank8 it’s not worth to be full int just for this one buff. Rank8 circle has no good options for dps or buffer so sage synergized well with a safe full tank build. Rank9 makes it worth to take int for both thauma2 and enchanter2 and amplify party damage output making more parties viable.
Rank8 began last year before dmg rebalance too, where everyone without enough con or non-clerics just got one-shot by mobs on high level maps, favoring tank supports and missile hole