I don't "get" the bullet time implementation in MP3. Sometimes I kill someone and get some back, sometimes I kill someone and don't. Shoot Dodge works without any bullet time at all. Sometimes it just regens a little bit for no reason and other times I have a full meter right out of a cutscene. There doesn't seem to be any rhyme or reason to it. I observe the crazy particle effects and stuff much more while in bullet time but I get to use BT so sparingly for extended periods that I probably miss a lot of it.
Playing: The Witcher 3, Bloodborne, Secret of Mana Watching: X-Files, Mad Men, Mad Max Fury Road