The damage you take is still fluff damage, it will take the same amount of heal to get the relative HP back up. -20%~ damage from hits is barely noticeable if you couple to the fact that no auto hits for more than 5k each (you probably just do 2-4 parry/block every min or so), the comparison tickles even more when you have 28k+ in i240. The only difference in this game vs many other games is the existence of timed and occasional tank busters. This greatly diminishes the point of blocking/parrying attacks as it's not reliable enough to stack.
You forgot to mention the PLD/MNK for str/int debuff. Also PLD for A8S, releasing healers from healing you to full (unlike DRK) for the Onslaughter's tank buster and the last Final Punch combo.
No Ninja is DPS loss. RoH is only a DPS loss when your OT (WAR) keeps using BB over and over, no other classes do a shit tonnes of aggro that you need to keep RoH-ing for nuts.
This is still closely related to your co-tank and your NIN. NIN giving Shades after swap is too good to miss. It's only a loss if you keep swapping for no reason, PLD being the only job that gets shafted so badly for that department.
HG simplifies most of the mechanics on the healers when you compare to DRK since you have DRK/PLD being the current meta MT. The moment you use it, healers can focus on other matters more. Other than that, any tank can do whatever PLD can do and DRK is still favourable for the veteran raiders due to the overall higher DPS it can contribute.
This one is dependent on the fights you are in and how comfortable you are. A5S doesn't have magical tank buster. A6S technically has some, but they are quite easy to do without so you are better off using it to mitigate other damages like the green balls. A7S is the same as A5S. A8S also use it for green balls (if you are doing the running) and tanking flamethrowers (does it even reduce that damage? because I just pop it whenever I can) and also soaking mines.