Been thinking about this. Really groups spells are a convenience - so we don't have to cast something 6 times. There are annoyances between some that are single and some that are group only. Because group versions are higher they are affected by focus effects to a lesser extent have to wait to level up to get them etc.
Wouldn't it be great to only have single target spells in the spellbook, but if I was to press a key before casting a beneficial spell it was 3* the mana cost and affected everyone in the group within 200 units of you.
Wouldn't that simplify the game such a lot.