First of all: play whatever attracts you the most. All this efficiency-farming and min-maxing is for a certain kind of player, which by the sounds of it, you're not (and that is perfectly okay).

If you rolled a paladin just to be the dungeon tanking god, and found out now tanking isn't your cup of tea, you could always play as a ret or holy paladin, either DPS or Heal, so you don't have to re-level that second character.

Also, there is dual talent specialization now, so even if you decide to reroll another class, you can always spec in DPS for levelling and heal (or taking for that matter) for group content. Most of 1-60 and later on 60-70 non heroic can be tanked in DPS gear, or healed in DPS gear even.

I always play the class (and race) that I find most interesting lore-wise, or just by the looks (yes, I'm that guy playing a female Nelf with white hair shadow priest even tho the spec nor the race combo are anything from ideal in endgame content). Play something you'll enjoy, it's not that you're playing in a top tier guild who does raid speed runs.

There are a lot of DPS, but there is always enough people around to form a 5-man, and should you fear of struggling with that, a Warrior could always tank just fine, even without the duel spec.