Reason tank DPS stat was changed to STR
The new weakness penalty imposed by dying is -25%/-50% to STR/DEX/MND/INT. This limits damage dealt and HP healed, while keeping HP and MP values intact (previously was a 30% penalty to both, which made surviving mechanics after raising from a death, exceedingly hard). Since the new changes, tanks' damage is calculated with STR in mind, so that when tanks die, they incur the same damage penalty as DPS jobs do.
If damage stat was changed back to VIT, then when tanks get raised they would suffer virtually no penalty; e.g. their HP won't be affected (since that's been abolished), and since weakness doesn't affect VIT, their damage won't be affected. Making it a .45/.45 split still means tanks would only suffer half the penalty as other roles.
If they wanted to change this, they could instead of making Weakness affect main attributes, simply make it a 2 minute status that directly lowers damage dealt and healing potency down by 25%/50%, since there are already "Damage Down" and "Healing Potency Down" debuffs.