FM Stances help

[Hwannn]

Im finding it hard to keep the ice stance when the enemy is doing an animation where you cant attack him... how can i use my frost sheath if the animation last more than 10 seconds and im no able to use my frost skills at all ? 

Yeah this happened to me once with slashimi at Blackram supply chain and i felt so stupid since i tried to divine veil to protect my allies from the projectiles but i wasnt able to use the ice block

Some tips when this happens ?

*i know you can switch with E or Q, but what if i have already used my E*