yes, you are quite right, tanking is not quantum physics or playing metal. You do not need a doctorate to play nor do you need years of practice.
It's a game, it's meant to be easy. Yet, you have people like the OP that think it's too hard, and people like the one above think it's too easy, the trick here is finding the right balance.
The poster above me mention DPS rotation and tank switch, but the role the tank go farther than that. There is no doubt in my mind that the above poster is a good player, but maybe not a good teacher. DPS rotaion for a tank must be automatic, a tank must go through his rotation without thinking. It is ok if he makes mistake in the rotation, if he use telekinetic throw with only 2 stacks of harnessed shadow, use project without proc, his job is not to maximize dps output, though it's good if he does.
While dps role is just that, go through their rotation while avoiding stuff on the ground, the tank role is far more important.
A tank (good one that is) must be aware of his surrounding, his position and those of is teammate. He must anticipate and react. When positioning a boss, he minds that there will be dps behind the boss. is there are mezzed mob, you can use slow time but not force breach, don't forget kick, stun. He does look at the combat zone, aware of the position of every raid member, aware of the strat, he also watch closely his own life because of his role, he is meant to take a punishement and may very much die, not from hiw own mistake, not from an aoe he miss to avoid, but simply because the boss deal more damage than he receives heal. he must be ready to use defensive cooldown.
And yes, knowk back are part of his awareness and anticipation.
PS: and by the way WoW warrior tank rotation is
Shield slam // Revenge // Devastate while maintening long cooldown debuff (thunderclap and demo shout), that 5 key that will be the only one you need to clear all the raid content in highest difficulty mode.
Some tank throw in shockwave with 3 stack of thunderclap, but it isn't necessary really. How simple is that?
I don't even begin to talk about paladin or druid rotation.
PS2: you forget dark ward in your rotation.
Whilst I agree with everything you posted, the general implication of this thread is that holding aggro in this game as a tank is difficult and this is exacerbated by knockbacks and stuns from NPCs. I was simply disagreeing with that general sentiment as I believe that the basic task of holding aggro in this game is mindnumbingly simple.
Sentinel does 1600DPS generating 1600 Threat per second.
Tank puts guard on sentinel, transfering 25% threat: Tank now has 400 threat per second, Sentinel has 1200 threat per second.
This means that as a tank, I only need to generate 800 TPS to stay top of the table. Due to tank stances giving me 200% threat per point of damage, I actually only need to do 400 DPS per second as a tank to stay top of the table against a sentinel doing 1600 DPS!!!
Should I fail to be doing 400DPS during a fight, I can always use one of two taunts which not only snaps aggro on to me, but places me 30% above the person at the top of the table, giving me a 30% buffer. the later I am in the fight, the larger that buffer is going to be.
Thats what I mean about it being faceroll easy. Ofc, I also agree with you that to be a good tank requires much more, especially regarding good judgement of who you want to drain threat from, placement of mobs, when to AoE taunt and when not to, when to use defensive cooldowns etc. However, in comparison to other MMOs that I've played, the core mechanics of tanking i.e. holding aggro and mitigating damage is excessively easy.