They hit a hardened target already on the defensive from a siege and came away with many channelers, probably on par with their losses. The lost a lot of to'raken but who cares because they will almost certainly have Travelling as soon as they break Elaida, assuming she's the only one in the crowd they caught who knew it.

The killed/captured numerous AS, and probably replenished their own losses or near to it. I'd hardly call it a great success but definetly not a defeat, they weren't trying to take the tower, it was a raid, probably designed more a sa fear attack then for specific tangible military gains.

When they get back to Ebou Dar, they will have numerous AS, not least of which being the leader of the AS, to parade as a great victory to their forces. From their POV getting Elaida and other AS is like capturing the leaders of a terrorist cell. Just getting Travelling would have been worth the entire force being obliterated and coming back otherwise empty-handed. Could have gone better, but it was definetly a military success.