Overall, I enjoy paladin but do agree with some of your points. While it isn't very complex, it does have multiple rotations and situational cooldowns - just like other classes. They are just really simple. Sword Oath as is stands right now, is generally useless. Our cross-class abilities are generally useless as well.

I don't really see the need for an MP "stance" because we currently have the Riot Combo which regens enough MP to continue on with Flash. And people over-simplify the combos imo. It's not like you just run up and start Halone, you'd want Fight or Flight and Bloodbath up, probably hit Circle of Scorn for the damage tick and quick aggro, cycle in Spirits Within on cooldown, and you'd want to manage your DR on Flash to keep Blind up as much as possible. If there are two enemies or random single adds you'd want to split the combo and tab target through the aggro list as well, managing aggro when needed, on top of managing Rampart or Conv etc. depending on the situation. Three of more, you'd want to keep up your CoS, Flash, and Riot Combo for MP regen. This is on top of positional awareness and mechanic avoidance. You end up with something more like:

Single Pull: FoF > BB > Lob > CoS > SW > Flash > Halone Combo (cycling in Flash for blind, SW on cooldown, CoS on cooldown, Rampart/Conv/Bulwark etc when applicable)
Multiple: FoF > BB > Lob > CoS > Some defensive CD > Flash (till aggro is solid) > Riot Combo (same as above, SW/CoS on cooldown, def CDs where applicable)

That said, it's not all that complicated, but it's not "spam 1, 2, 3" like people seem to think. Tanking in general, regardless of the class, presents a lot of challenges that DPS simply don't have to deal with. And when we screw up it's usually a wipe, so there's more pressure. We get the brunt of enemy mechanics (in most fights), we have to deal with placement, we have to cycle mobs and pay attention to hate levels, mark for DPS (when applicable), and we set the pace for runs in dungeons. The addition of these challenges is probably why they made the actual gameplay a bit more simple for the tanks. You also have to have some boss knowledge and know when to use things like Sentinel and Hallowed Ground - particularly on big hits like from Titan's MB.

I think those are the challenges that make Paladin "fun" for me - but those come with the territory for tanks and are not exclusive to paladins. The play style is rather simple but keeping the big picture in mind I'm fine with how they are.