The Paladin gets a bad rap, and it is half deserved and half not. Levelling is slow because your damage is low, but you almost never die, since you wear plate, heal yourself, and have a bubble that makes you invincible for a few seconds. You can plow through a grind that would kill a Mage three times over, just not quickly. Auto attack a mob, Seal and Judge, heal up, repeat. It is the definition of slow and steady.
At 60 the Paladin is a healer and a buff machine, and that buffing is where the class earns its keep. Blessings of Kings, Might, Wisdom, and Salvation are handed out to the whole raid and dramatically boost everyone's performance. Salvation alone, by reducing threat, lets your DPS go all out without pulling aggro. A raid with a full set of Paladins blessing every group is a much stronger raid, even if the Paladins themselves never top a meter.
People meme on the Paladin as a glorified buff bot, and there is truth to it, but the bubble hearth is undefeated, Lay on Hands can save a run by fully healing a tank from the brink, and a well played Holy Paladin is a rock solid tank healer. You are the unsung backbone, and any Alliance raid that has tried going without Paladins learns to appreciate them fast.