I think spells coming online too late should be handled 2 ways. First, half casters should be getting more unique spells. Because they are unique, they should be a bit "ahead" of the power curve than the level would suggest.I'm not sure how you are judging this; an issue with half casters is that they get spells too late to be that useful. One of the Fey Wanderer's party pieces is Summon Fey - but on a level 11 battlefield AC 15, 30hp is a speed bump (the CR 11 Roc has +13 to hit and multiple attacks averaging over 20 damage)
Second, I would like to see a come back of the 3.X spell progression at different rates.
For example: Command Plants could be learned by Rangers starting at 3rd level, but Druids wouldn't learn it until 4th level. This would let half casters get spells "early", or at least less late.