Sorry for my scepticism, but I doubt you did finish the mission. I'm looking at the demos from b4 (since, even if you did slight undocumented changes on rc3, most of the changes on Expert were on b4) and I've only found one demo with Expert being beaten on rc1. But I do not have the rc1 version of the map and I can't find a download link here, so I can't watch the demo. Can anyone give a link where this version of the map can be downloaded please ?
Also, I'm speaking about demos on the Potato's server, but maybe you didn't do your testing there ? Do you have a video or demo of one of those play session where you beat the most recent version of the Expert mission ? I don't think you have one, since I don't believe anyone would think about recording their playtesting sessions.
About your definition of Expert : we all have our idea of what should be THE Expert MvM mission. But by the end of the day, our definitions doesn't matter, only the official Expert missions are what is the closest to the "official" Expert difficulty level. And I'm sure everyone can agree that Teien's Expert mission isn't similar in difficulty to these missions. And I've said it in my review : if your mission wasn't tagged Expert, but an other difficulty above that you would have invented, it would have been better.
I did play the earlier versions of the map, and back then the Expert mission was much, much easier. I do not know exactly at which point the mission got a bit spike of difficulty added tho, and if you played it.