Ive checked better today, the mouse pointer stays unchanging, when you cast any spell - for three full seconds. So you cannot select another spell or a skill during that time.

Im not sure what could be the reason for it, maybe... to prevent players to throw several spells too fast..? or something?

Seeing how its turn based combat and engine is performing really well otherwise... it doesnt seem it would need such delay. If that could be lowered down it would be great.