Having played as a paladin, I can say that I really enjoyed the class, however there are a few shortcomings. I won't bother to mention skill cool-downs or overpowered skills, as it's fairly obvious they've all been said already. However, I will say that the Paladin is definitely overpowered. When I was on the Werewolf Berserker quest, for example, I was able to solo the Berserkers thanks to a combination of Divine Strike and Strength of the Gods. While I believe something like this SHOULD be possible, I think it should be possible for EVERYONE, and should probably be a fair bit harder to do. I do believe that Armor of Thorns should last longer; for me, at least, it activated maybe twice or thrice on any given opponent in the minute it was active. Either that, or up its damage slightly. Just slightly. Also, perhaps a few skills should be harder to get... I got Divine Strike Lv. 3 when I hit Level 4. While it's not an especially powerful skill, it illustrates my point: once the first level of a skill is obtained, you can max it out quickly, making skills capable of becoming very powerful very early. Beyond that, I don't have much else to say on the Paladin.
Limitations are for those who don't know any better... With the right mindset, you can throw fireballs. Oh, wait, that's me.... >:)