Rebuke is hilariously underpowered.
While we fix it, can we also limit Smites to 1 per turn? In fact, can we limit all spells to 1 per turn, as per the actual rules? At least on Balanced and Tactician. Double and triple Fireballs are just as dumb as unloading 4 Smites per turn. These remove all challenge from combat effectively as much as Shoving bosses into chasms does.
In 5e, there is no rule against using Divine Smite on every attack a Paladin lands, and yes, it is immensely powerful. While this is true of the DIvine Smite Paladin class feature, the same should not be said of *all* smite spells that even other classes get access to. Regarding casting multiple spells requiring a full action in a single turn, the only way you should be able to do this is with the Fighter's Action Surge. If the Haste spell is allowing this, that is a significant oversight.