The best thing about W&W is there are a number of ways to play, and all of them are right. So don't worry too much about developing your characters "right". Whatever way you develop them will be right. Other options are just different.
Personally, I upgrade my warriors ASAP. They get zero benefit from remaining warriors, so I move 'em to Barbarians first, and then onward. That matches with your thinking, so I like you
Why barbarians and not paladins? Because they get those barbarian HP at the beginning of the game, and not later. HP are assigned by re-rolling your HP when you increase levels. If the reroll is higher than your current HP total, you get a boost to the new total. If the reroll is lower, you get one point. So I'd prefer to get all those HP on a 10th level barbarian so that when he (or she) is a lowly warlock, they won't be killed by a small pack of worgurs.
Now, I have to confess that if you look at Missy's story, around chapter five or so, she never got that fabled HP bonus. I think out of ten levels, she got more than 9 HP perhaps twice. Still, it works in theory