Bard Ult Interactions

I've been playing Bard a lot recently and I've noticed what seems to be a bug with his ult interacting with other ults/abilities.

1. I ulted an MF who was currently ulting, and MF got about 2 more ticks of her ult off while in stasis which killed my ADC =(
2. Ulted a Lux whom I saw retreating from a fight, clearly about to laser my precious ADC. I ulted the Lux the instant her ult animation started, yet her laser of doom shot while she was in stasis.
3. Lastly, a Tristana literally E'd while in stasis. Her shiny golden stasis statue rocket jumped away. I actually saw another example of this in one of Realm Games' "Random LoL Moments," videos.

Is this supposed to work this way with certain ults? Please Riot, address my new favorite champion !