Lets get some things straight here. For one your supposed experience with tanking in other games does not directly translate to experience or knowledge to tanking in this game beyond the basic principals. Secondly you're trying to manufacture situations that are not at the heart of discussion here.

Post-50 you can run into a gear disparity that requires DPS to play sub-optimally in order to facilitate a smoother run. This is not the general rule of thumb and not the discussion that's being had. What we're discussing is a pairing of relatively equally geared players doing content together. Or even more specifically every dungeon pre-50. As that is where the greatest contention is, about a Tank's ability to keep hate, among the playerbase. The reality is that a good tank does not need to mark because there, generally, is not a kill order for trash pulls. The only rule that a DPS needs to follow is that they should not be attacking a target that has not been attacked/claimed by the tank yet. Meaning on pull the first target to be attacked should be the tomahawked/lobbed target and after that it's open season. A tank, playing optimally, will be able to hold the entire pack so that the DPS can apply pressure to any individual mob without worry.

Notice that the only one here with a toxic attitude is you. You are deliberately poisoning the attitude of the playerbase and teaching new and upcoming tanks that they can't be more than they are now. That they should settle for mediocrity and to ignore the advice of actually skilled and experienced tanks for this game. The FACT of the matter is that GOOD tanks do not need to mark for trash pulls. Are all tanks good? No. But they should be working towards the point that they will become good. And constantly babying them is not going to make them improve.