Originally, it was like the Magic the Gathering deck archetypes were you have Aggro decks, control decks and combo decks. I decided to use that idea for magic type because it seemed fun and was better then have just skills.
As for do they need to be...probably not but I kind of have already done it so no point in going back and changing everything. Honestly, looking at it now, maybe it was not the best idea to do it that way.