Well you've basically picked up on all the shortcomings yourself.

The biggest one is how MAD it is.
Yes you can eventually get to some halfway reasonable stats. But you're wading through treacle for a LOT of levels beforehand. For this reason alone, paladin/cleric is best served when you've rolled for stats and have been lucky enough to get a handful of above average rolls.
Personally I'd rather see Paladin as a WIS class because cleric is an obviously better fit for multiclassing, and considerably less OP than sorcadin. But there we are.

And yeah, secondly you've got a painfully late second attack. So you start out being a pretty meh cleric, then you wait an age before becoming an even more meh paladin.
The last 5 levels or so will be fun, but then almost any PC at levels 15 and up will have enough juice in the tank to be a laugh even if they're not optimised.

If the concept is fun and you think you'll enjoy playing it then go for it. But I've tried to make this multiclass work before as well amd it was just too frustrating. It feels behind the curve for way too much of the game.