Mustrum_Ridcully
Legend
Yep, I noticed this one when I created a Halfling Paladin with the Mark of Healing.Add Hospitaler for triple Cha at Paragon.
Not sure if I want this for my Kalashatar paladin again or not... I traded Healing Hands for Virtuous Recovery last level under the assumption that it would prevent more damage than this heals most days.

I don't know if it's overpowered. It might be "overfocused". I would also suggest the Cleric multiclass feat that grants you Healers Lore. (Interestingly, the Character Builder in the current version allows taking multiple multiclass feats from the same class, but does add the house rule note? How can that be?)
I mean, generally, you might get benefits from Charisma from different powers and special abilities, but they would go to different effects. Maybe you get an ability that allows you to add Charisma to Lay on Hands Healing, an abilty that allows you to add Charisma to damage once per encounter, and an ability that allows you to add Charisma to a defense once per encounter..
Would this be overpowered, too, because you find a way to milk your Charisma Bonus from multiple sources?
Of course, it is reminiscent of various special abilities in 3E that allowed to add "non-standard" ability scores to Armor Class. But this was usually problematic due to the frontloadedness of the given classes - it grants you lots of good features at 1st level to make the character concept behind the class work, but if you multiclass, you get more out of it then intended.
But in this case, you take discrete abilities - feats, powers or paragon paths that you can't "cherry pick" from an entire suite of abilities that is normally linked together but through your "trick" is not. Multiclass feats are designed to give you specific abilities and stay balanced. Paragon Paths can't be cherry picked - pick all or pick nothing. Normal Feats are all assumed to be fair game once you qualify for them, and the power boost gained by them shouldn't break anything.
So, I think it's not a problem of overpowered abilities. It is a problem of "overfocusing". But that doesn't have to mean it's too powerful. You gain in one area, but don't get the opportunity to gain in another one. Your Lay on Hands really counts for a lot now, but your Divine Challenge might not count as much.