Overpowered if we started with an early WoW patch. But for 1.12:
Actually very strong for (solo) leveling up to around level 40.
Level 40-60 is where the painful slog begins because Paladins don't get a lot of DPS increases via talents or abilities and don't scale very well with gear either - unlike e.g. Warriors. Have fun questing, farming and grinding reputations without friends or a Mage/Hunter alt!
Endgame: awesome Healers and Buff Bots. That's it.
Sure, you can make Rets/Prots/Shockadins work up to a certain level and with tailored raid/group composition but it requires unreasonable effort when you can just roll a Warrior or true DPS class - or play the better Classic WoW that is TBC.
'But Jimmy, Classic was easy - you don't have to minmax!' Yes, Timmy, we don't have to. But please, put at least 13 points into Holy and wear your cloth gear so you can be somewhat useful in your Ret spec, mhkay?
(btw 13/8/30 was a pretty solid hybrid spec for pre-60 overall questing and dungeoneering)