What is the prioritization supposed to be for Fioras Q "Lunge"? Is this a bug?

https://www.reddit.com/r/FioraMains/comments/5ehpmw/fiora_is_bugged/

http://plays.tv/video/5835af3e7b41e3a860/fiora-bug

http://plays.tv/video/5835b07815a9300b5b/fiora-bug-2

What is the prioritization order suppose to be for Fioras Q lunge?

Vital > Champion > low HP minion > Minion

or

Vital > Low HP target > Champion > minion

Or is the prioritization something different?

I feel like it has been "Vital > Champion > low HP minion > Minion" for quite some time (several months) but just wanted to make sure this is the correct prioritization.