BLM possibly bugged?

[rowrow]

Tested it by leashing mobs. When the mob walks back to its original position, it temporarily becomes invulnerable. I had 3 stacks of fire with about 5-6 secs left then swiftcasted Blizzard 3. I ended up with neither buff.

Starting the cast itself doesn't remove the buff since you can move and cancel the cast and you won't lose your current stacks.