The Runemaster passive node “Never late” does not give its buff consistently when using flame rush. This effect occurs with any kind of flame rush, channelled, non-channelled, casting other spells or not. Occasionally it works on the first couple of casts of flame rush after putting the points into the passive tree.
The video shows the buff working with teleport but not appearing with flame rush, the flame rush in the video is not specialised in anyway. Once I try with 4 points in the passive it works as intended.