Paladins have changed a lot over the course of the game. Originally, we were intended to just be healers with some additional specs for leveling. Then we were suddenly able to tank and everything was about reflective damage with a dozen or more things hitting you at once with a DPS spec that was usually relegated to the PvP scene instead of in raids. Finally, we've reached a point where all three specs are pretty viable in both PvE and PvP content. That isn't to say that they're the most phenomenal things to ever appear for those particular parts of the game but that we can still be competitive no matter which spec we choose.
The problem with our class is a lack of tools. While our melee components were slowly built out of what was intended to be a healing support class, we've still got a lot of vestiges of the old days tacked to us. Sure, we had a fairly large overhaul in how a lot of our mechanics worked at the start of Wrath of the Lich King, but that isn't to say we're perfect yet. In fact, we need a few more tools in order to make it in Cataclysm.