I've just had a very quick gander and a few things struck me.
I think you should change Indomitable to automatically making a save. It's simpler and cooler. I'd also like to see the fighter getting additional ASIs.
The spell progression list for full casters looks a bit odd. Given it takes 7 levels to get an additional 6th level slot I think extra 9th level slots should come in much earlier, at 24th level. So one 9th level slot at 17th level, two at 24th, three at 31st, and four at 38th. If you made it every 8 levels, you'd have one at 17th, two at 25th, three at 33rd, and you could give the fourth a level early at 40th. As an alternative, you might consider adding 10th+ level slots for the purposes of casting spells at higher levels.
Rather than adding higher level spells to the Ranger and Paladin, how about making the spells they cast more powerful? E.g. at 21st level when smiting the damage die increases to 1d8 normally, and 1d10 for specials, with further increases as the Paladin levels.