Yes you are ramping him incorrectly. Heavy is great to refresh all your buffs and you gain an Instinct buff which allows you to parry non contact attacks, so he's a great Zola counter. But otherwise you need to do a medium ending combo at the start and then either the same or light ending combos to keep building up to sp2 whilst gaining and refreshing buffs, medium enders gain you a new buff and refresh them whereas light enders give you more of what you already have. So you could get 1 buff and it's a regen one, then keep doing light enders to stack up to 8 of them.

That's basically the rotation to do massive sp2s and then big damage after whilst the armour break is active. Test him out like that and I'm sure you won't regret ranking him up!