Despite voting that I hate it, I don't think I actually hate it (though it's not fantastic in the group you have, particularly since Paladins are great secondary defenders, but not perfect primary defenders.
Aside from the obvious:
The stat synergy is great, but I don't know why you're picking off-stat powers. You should be able to do what you want while sticking to Cha primary, Str secondary powers (or no secondary) powers.
Paladin plus at-will close blast is strong.
I'd go for plate prof over Dragon Soul, I think--as off the bat it gives you +5 AC--and even if you made other choices (dragonborn, 13 con for hide armor) the max AC you could get from hybrid sorc + hide without gimping Cha is 17--for two feats instead of one (three, including the one you lose for not being human). OTOH, if you stick with cloth (with Unarmed Agility, natch) you can wear armor that lets you use Blazing Starfall on a marked enemy at a distance while hanging out next to a completely different enemy and getting in his face (without drawing an OA), so there's that.
A Paladin/sorc really needs to decide whether you're a heavily armored area striker or a defender with an at will close blast. IMO, you're much better off with the latter, particularly with your group, so you want to pick your powers and feats to be better able to defend yourself and others--and reserve the sorcerer powers for the points where the best way to defend your group is to take enemies (mostly minions) off the board. As such, I'd go for Ardent Strike and Burning Spray for sure, as those cover "lock an extra enemy down" and "blast some enemies" nicely. As a human, Blazing Starfall is fine to cover your bases (particularly since paladins and radiant go together).
Mighty Challenge isn't on your list. It should be; your Challenge is rather wimpy.