So we are going to get 5 new skill points, but there's not much to do with them.
Introducing completely new skill or 2 for each class would throw the balance off completely for some time.
I hope STS has some solution in mind already but I've come with this.

For each skill, we can identify the most useless upgrade (bomb for veil or health regen on heal comes to mind).
Let's make this upgrade actually useful, and cost 2 skill points.
Let me show this on Sorcerer class:
Fireball: Scorch -> enemies chance to hit 50% for 5 seconds
Frost: Ice patch -> pulls more enemies once triggered
Clock: bomb at end -> stuns surviving enemies
Shield: scatter -> 20% of incoming damage is reflected to enemies
Heal: health regen -> seriously buffed, includes mana as well; mana regen can be replaced with e.g. something like shadow veil
Curse: 10% damage -> also reduce incoming damage
Gale: Protective Current -> add armor on uncharged gale

I'm pretty sure this suggestion could be worked into an actual solution.