Never own AT gear, so don't know what the mids sound like. But I like the restrained treble part. Like you, I'm sensitive to sibilance and peaky treble.
How's the stage on them?
Audio Technica is famous for silky mids especially female singers and the WS1100 has that signature sound. Soundstage is good for closed cans and the slightly tilted pads help too. Don't expect AD900X level of soundstage and imaging.