First I have played through the UTUBE preview of the next version. It is very impressive.

I have suggestions that would improve the playability of the game.

Suggestion one

Allocate each defensive spell a key on the keyboard rather than having to navigate between them.

Suggestion two.
The problem is when you are fighting a powerfull monster using icons of the defender and pounding the monster with masses of time bombs. When the invulnerability created by an icon of the defender wears off you have to scramble to use the next one and then switch back to the time bombs.
My initial thought was to use a hot key for icons of the defender. This would make life much easier.
Then I thought of a change which fits in with the philosophy of the game.

In addition to the existing initial spell create an invulnerability spell for all three classes available at start of game which works if you have icons of the defender and uses one.