ya'll hating on paladins
Paladins don't have to worry about moving fast, not when they can throw their shields and burn the ground. Not to mention that AoE damage is their basic aggro ability. Not to mention they can heal an ally in danger, as well as support your group in various ways.
Not to mention the fact that they have like 5 mitigation skills on either super low CDs, or relatively low cooldowns compared to shield block which has like a 50 minute CD in relative comparison.
Paladins Rock.
I mean, no tank HAS to move fast, but you generally want to, if only to keep the group moving. Plus, movement speed has a solid impact on Mythic+ timers, you gain a non-negligible amount of time if your tank can always be the first one to the next pull. But more than anything, moving fast/being mobile is FUN, while being slow is decidedly less fun (at least for me personally). Not only do Prot pal have low mobility, but they are virtually rooted to their small Conc circle for optimal mitigation, it just feels limiting. And sure, they can throw their shield, and Judge, but if adds spawn when shield is on CD, you are actually pretty lacking in tools to pick up ranged mobs, I think paladin is the only tank that doesn't have a no-CD ranged ability to pick up adds, (technically DH is 2 GCD long CD) while also being the least mobile.
Now, like you said, Prot Pal is still awesome. Lots of CDs, TONS of utility, great healing for self and others, and awesome damage. But that slow prodding movement really hurts the fun of the class for me, and as a tank being mobile and able to quickly get between mobs is important to me. DK is also very immobile, but at least they can grip the mobs to them. Not sure where you're getting the "5 mitigation skills on super low CD", pally CDs all have kind of long CDs. Artifact ability is great at 60 seconds, but AD is 2 minutes and everything else they have is 5+, their defensives are on the longer recharge time end (ShotR doesn't count as a defensive, its just the standard AM every tank has). Still very strong though. Strange to compare to warriors too, who have Shield Block on a 12 second recharge vs ShotR's 16 seconds, Shield Wall on a 4 minute recharge versus GotAK's 5 minutes, and wars also have Demo Shout (1.5 min) Last Stand (3 min) and Artifact Ability (45 seconds), pretty much shorter than pally CD recharges across the board. Generally less powerful though for sure.
Honestly though, the biggest problem with prot pally? Blessed fucking hammer. Fuck this ability and whoever designed it. I know this doesn't bother everyone as much as it bothers me, but I HATE constantly spamming those spinning hammers. I hate the sound, I hate the graphic, I hate the frequency at which you have to use the ability, and most of all, I hate that it is so powerful that you would have to be a fool not to use it. God, I would probably play Prot Pal despite the movement if this one ability didn't exist.
