Yeah maybe it had been a number of years since a hostile abduction of a mandati, and they just couldn't fully understand the consequences. They had grown bold in their arrogance and undisputed place at the top of the schoolmen hierarchy. We see this in TTT when they are getting wrecked by the primaries. Too much self confidence leading to disaster.
Iyokus was certainly over matched at that point. Considering jt took all those men to subdue him, 3 is just paltry . Clearly in the event of his escape he was not going to get re captured.
Like you said, they underestimated him twice, each time a disaster. Iyokus learned, Eli did not.. the second time they lost the sorcerers of rank, a contingent of javreh, and inevitably a handful of trinkets.
Still would love to have seen a concert of gnosis users. The concert of ss made a flaming tornado and multi headed dragons, I imagine the geometries and abstractions created by a gnostic concert would be mind bending. Theorems of layed magic simple too complex for one mind to complete.