Funny that you mention the fire rain spell. I was about to reply that you CAN learn and do it, but after checking it seems i forgot it for the loot tables. Theres still 7 other spells to find. However the sorceress companion can learn it early on and can use it on groups of enemies.
Working on the lag and pushed out a new build not long ago, that may or may not mitigate that.
Thanks for playing and the feedback. Will keep these things in mind!