Ninja works just fine for me on PC, and PS4. I suffer from no lag at all.
As for the Bard I cant really speak for, but the Paladin is working as intended. It's DPS although the worst of the 3 tanks, I feel like it's the best beginner tanking experience. You have the easiest skill set which allows beginners to the game, and beginners to the role a chance to learn basics of tanking. You're flooded with a ton of Cooldowns to help keep you alive. Although I've yet to do Savage Alexander, I can say that the Paladin hardly suffers. DPS is only a tanks secondary role, and no DPS should ever complain about a tank unless that tank fails to hold hate, which is entirely up to the players skill; not the DPS being dished.
Should you level these Jobs? completely up to you.

Right now it seems Summoner is the god tier of DPS but I must say, playing a Ninja I am constantly complimented on my dps rates in pretty much every daily roulette, trial, and so on so-forth.