A lot of the current issues are "group" problems and not necessarily tank problems. From what you're describing, that's what it sounds like. It was easy for people to get away with a lot of that stuff at the tail end of Wrath. Now we're paying the price for the laziness inherited from that. Myself and a couple others had talked at length about what we termed, lazy dps. Lazy in the sense that they were not fully mentally engaged and aware. It shone through mainly on certain fights in ICC where it was critical for dps to move or switch targets rapidly.
My suggestion:Tell the group what you need. Speak up. If someone gives you heartache over it and tells you to stop being a QQ tank, kick them, because honestly, they're not truly interested in finishing the dungeon anyway. YOU know how you function best as a tank and you're learning rapidly what you can and can't handle currently. If the group is sincerely interested in succeeding, they will adjust to make the encounter a win. Need a moment to set aggro and get vengeance up? Say it. Takes 10 seconds to explain that pre-fight and it takes minutes to recover post wipe.
Or, resort back to the old rule: You pull it, you tank it.
Is it nice? No. But, having a dps pulling another group while still currently engaged in combat with another group, they are initiating the wipe, not you!
On the flip side of this, do your homework. Look at an encounter and plot out how you want to tackle it.
Quick example: group has a warrior tank, DK dps (frost), hunter, mage, and shaman healer. Set of 4 mobs, 2 melee, 1 mage, 1 heals. I'd approach this by having the hunter set their frost trap on the healer, with the mage following up rapidly with a poly on the caster, and the shaman popping hex on the closest melee after that. Why? The hunter's cc is location dependent. If the mage poly's first, the healer will likely move making it more difficult for the hunter to set their trap. I'd make it clear to the DK at the start of the dungeon (and they should know this) that they shouldn't use DnD and if they have howling blast, make sure it's only used facing away from cc'ed mobs and after I am able to get a rend + thunderclap in to cement aggro. On the polymorph, I'd also have the mage run back towards me so that the mobs head my way. As the melee start charging in, the shaman should be able to slap hex on the closer mob, reducing the pull to a one on one for the start.
Is this challenging in a PUG? Yup! Unless you communicate clearly. It's definitely easier with a guild run or with people who play consistently together. The key is still communication. Those people who are willing to communicate and cooperate, they're playing to win. Those who aren't, you're better off without them. Even if they have blisteringly awesome dps.....they are a liability because they are not working with the group to accomplish the same goal. Oh, but what if they're really a really, really, really, good player (kinda Zoolander-esque there) and know the encounter? Answer: they are still fail because if they know something that will impact the group or will help the group succeed in an encounter, but don't share it, they are still not working towards the goal of successfully completing the encounter.
No one tanks in a void.........