All that said and with that concept in mind, no, it doesn't really seem logical to think that /cast !Deterrence would help here, but you never know. Sometimes things function strange, especially if they are new. But obv. we've got past the fact that it doesn't help.
Hopefully spam protection is baked into it as it wouldn't really make sense not to do it. I am aware of the datamined 0.8 second "cooldown" but you never know the intentions until it is actually live on the PTR. We will see - and if it for whatever reason doesn't make it, the castsequence should work just fine.