I loved the role of the Paladin in WoW vanilla (support class). In PvE it was a pain having to manually rebless the entire raid every 5 minutes and who thought it was a good idea to design a boss that demands someone that keeps spamming the decurse button throughout the encounter?? Besides those things I liked having more of a free role and aid wherever it was needed the most as opposed being designated to solely heal the main tank as a priest. In PVP I basically made the flag carrier invincible with blessing of freedom, decurse, heals, stun enemy players and of course popping bubble as soon as they realized it was better to kill me first! I had so much fun messing around in battlegrounds before they introduced resillience gear since I had top PvE gear and was pretty much unstoppable.
When they changed the healing mechanics from being about mana conservation to just constantly spam the heal button I got bored of it very quickly. In vanilla during farm bosses I had a blast aiming for most healing done while also being the person who had the least overheal done, I managed to do that a couple of times
I later rerolled to a DPS class because I wanted to keep pushing myself beyond merely downing a boss,
as a healer/tank you can't really do that but as a damage dealer you can always squeeze in more DPS if you perform better. Always striving for as high DPS as possible kept me on the edge of my seat and made even the most straight forward encounters fun to me.