The tank trait mastery actually nerfs tank damage by making STR worth less point per point than other jobs.
As someone who has been doing math work on tanks (and crafters), you're going to need to put some sources for that, because its something that nobody else is talking about.

tanks would be doing much closer to dps than they are now due to the fact they gained a TON of str on their accessories the instant SHB started on top of gaining huge potencies to their rotation due to SHB changes, yet were only seeing very minor gains to dps
Significantly more changed besides strength on accessories between 70 and 80. Tanks melded for those stats on accessories prior to this, so the actual gain stat-wise this expansion is almost negligible. You gain between 72 and 120 secondary stats per piece (since you're melding those and not mainstat), compared to the relative value of those slots in SB.

If you want to look purely at tank damage at 70 with everything re-melded, you can, but the relative difference isnt -20%.