I have no choice but to believe the current spell hotbar and interface just is a WIP.
Already when playing a wizard or cleric the bar is bloated to the point where you hardly can contain all of your spells on a single hotbar. It's only going to get worse as you unlock more spells, so I really hope something's done about this sooner rather than later.
Other CRPGs have already created perfectly functional UIs for this. There's no shame in letting yourself be inspired by those; you don't have to reinvent the wheel for everything.
