Been noticing this for a while - on magicka builds in PvE, if my stamina is full (over 9k in all cases) if my magicka pool is low, block fails. This is especially true on magwraden using ice staves ***without tri-focus***.E.g - if there are 0 skill points in the tri-focus passive, just having an ice staff equipped should NOT be using magicka to block!