The amusing thing about tanks is that there's a pretty noticeable dichotomy in how the role works, in 4 man and 8 man content. I'd argue that 4-man and 8-man tanking are very different skillsets. When you tank a 4-man the entire speed of the run is on you. Everyone wants the dungeon done as fast as possible if it's not release day and we're not all figuring out what's going on, especially in endgame dungeons. So it falls on the tank to understand the AoE potential of all classes, the relative gear of the DPS and healer, and then determine just how much to pull. Too slow and there's fifty-percent chance the BLM or WHM yells at you to 'go faster', or the BRD just runs ahead and starts shooting stuff. Too fast and you wipe and ultimately lose time. So there's a sweet spot. Cooldowns tend to be blown in bursts instead of rotation. Bosses are usually the 'easier' part if you have a jived run going.
In 8-man content it's just your duty to know your mechanics and enough about your ability rotation and cooldowns to not die while maybe contributing some DPS though outside of Coil the checks aren't tight enough for that to matter. And honestly? Tank-specific mechanics are really easy outside of a few like Garuda EX. Stand in one spot. Don't die. Dodge the telegraphed AoE. Swap when the boss hits X stacks on something. Pick up adds (Which comes naturally with practice, the exact cone of Overpower, the radius of Flash/Circle, ect). I can't think of a fight that demands a tank handle a lot more at once than just 'not dying' while occasionally re-positioning or Provoking. It's healers/DPS that get the worst, raid wiping mechanics. Landslides. Nails. Plumes. Ect. I'm only on SCoB so far but the 'most mechanics-heavy' fight that a tank can actively participate in would be T8 for me when I OT. There are a lot of mechanics there that I can take upon myself if I so choose (And in my DF attempts -I do so choose-). Otherwise.. Nah, tanking isn't 'hard' when you get in the right mindset for it and know your rotation and the bits of the fight which have relevant mechanics for you. 4-mans are almost more demanding in terms of on-the-spot decision making and adjustment/play.
I think a big reason many people gravitate to DPS is that personal responsibility is dispersed. In 4 mans you have another person that can also be put to blame if DPS fucks something up (Not that 4 mans have.. Anything a DPS can do to instantly wipe the group, 90% of the time). In 8 mans unless you have parsers in use and people actively paying attention you also can sometimes hide behind others in your role with silence when things go south (And people in DF don't like calling people out when they're DPS either, for some reason. Not even for parser-related things. Just repeatedly standing in fire).
Anywho, SAM. I think it'd be neat to have it, but I'm not entirely sure how many 'methods' of tanking this game can sustain at once. There are only so many constructs within the framework of the game's mechanics that can allow for diverse tank playstyles. PLD is '1-2-3 with 10 situational cooldowns to rotate through'. WAR is 'debuff combos, TP management, short term mitigation/healing tha tneeds to be used right before a big hit'. DRK is presumably going to be some form of self-heal/debuff with more of a magic flavor unless I'm remarkably wrong, which will be stepping on WAR's toes. They might well make DRK have self-harm too like in other FF games but that seems remarkably risky for a tank. Then again, it might make DRK the tank have a high skill ceiling which I would love to see. Who knows. SAM could concievably work as more of an 'evasion' tank like Druids or Monks do in WoW, but FF's tanking model is based mroe around threat/management than constant active mitigation. Or they could be a mobility focused Dexterity tank, able to zip around faster than the others but have a bit less mitigation as a result. I don't know. It'd be interesting to see a fourth tank job, certainly, that said. I also wonder if they'll always keep the 'all tanks share gear' paradigm. I hope they do with DRK, but when we get four, five tank jobs? Who's to say. It'd make gearing up shittier, certainly, with more RNG involved. Maybe they'll move to a token system then so all tanks get the 'same' token but can only get a piece of gear for two/three of the jobs instead of all of the tank jobs.
In 8-man content it's just your duty to know your mechanics and enough about your ability rotation and cooldowns to not die while maybe contributing some DPS though outside of Coil the checks aren't tight enough for that to matter. And honestly? Tank-specific mechanics are really easy outside of a few like Garuda EX. Stand in one spot. Don't die. Dodge the telegraphed AoE. Swap when the boss hits X stacks on something. Pick up adds (Which comes naturally with practice, the exact cone of Overpower, the radius of Flash/Circle, ect). I can't think of a fight that demands a tank handle a lot more at once than just 'not dying' while occasionally re-positioning or Provoking. It's healers/DPS that get the worst, raid wiping mechanics. Landslides. Nails. Plumes. Ect. I'm only on SCoB so far but the 'most mechanics-heavy' fight that a tank can actively participate in would be T8 for me when I OT. There are a lot of mechanics there that I can take upon myself if I so choose (And in my DF attempts -I do so choose-). Otherwise.. Nah, tanking isn't 'hard' when you get in the right mindset for it and know your rotation and the bits of the fight which have relevant mechanics for you. 4-mans are almost more demanding in terms of on-the-spot decision making and adjustment/play.
I think a big reason many people gravitate to DPS is that personal responsibility is dispersed. In 4 mans you have another person that can also be put to blame if DPS fucks something up (Not that 4 mans have.. Anything a DPS can do to instantly wipe the group, 90% of the time). In 8 mans unless you have parsers in use and people actively paying attention you also can sometimes hide behind others in your role with silence when things go south (And people in DF don't like calling people out when they're DPS either, for some reason. Not even for parser-related things. Just repeatedly standing in fire).
Anywho, SAM. I think it'd be neat to have it, but I'm not entirely sure how many 'methods' of tanking this game can sustain at once. There are only so many constructs within the framework of the game's mechanics that can allow for diverse tank playstyles. PLD is '1-2-3 with 10 situational cooldowns to rotate through'. WAR is 'debuff combos, TP management, short term mitigation/healing tha tneeds to be used right before a big hit'. DRK is presumably going to be some form of self-heal/debuff with more of a magic flavor unless I'm remarkably wrong, which will be stepping on WAR's toes. They might well make DRK have self-harm too like in other FF games but that seems remarkably risky for a tank. Then again, it might make DRK the tank have a high skill ceiling which I would love to see. Who knows. SAM could concievably work as more of an 'evasion' tank like Druids or Monks do in WoW, but FF's tanking model is based mroe around threat/management than constant active mitigation. Or they could be a mobility focused Dexterity tank, able to zip around faster than the others but have a bit less mitigation as a result. I don't know. It'd be interesting to see a fourth tank job, certainly, that said. I also wonder if they'll always keep the 'all tanks share gear' paradigm. I hope they do with DRK, but when we get four, five tank jobs? Who's to say. It'd make gearing up shittier, certainly, with more RNG involved. Maybe they'll move to a token system then so all tanks get the 'same' token but can only get a piece of gear for two/three of the jobs instead of all of the tank jobs.