Tanks:
Damage reduction (we used to have blocks, parries, physical defense buffs and raw mitigation, STR down, INT down), but all these differences caused major issues when fights did a different damage type. Thereafter, they were homogenized. But we always effectively had a 20% and 30-40% buff on tanks in some form or another, even if their attributes were slightly different.

Provoke. Because it's basically in every other MMO too.

An aoe attack to establish threat on multiple enemies, whether that is an AoE attack, a pure enmity effect like Flash or an AoE Provoke like Ultimatum was.

Healers:
Esuna

DPS:
At least 1 button that reduces the damage of an enemy.
At least 1 button that reduces the damage of multiple enemies.

All roles:
A ranged attack of some form is desirable for when not in melee range. If not, something like Monk has instead where it can charge up an attack, a gauge or do a long-distance melee attack.

(Note my lack of mention of heals. Since FFXIV has proven that healers don't need to actually have heals lol)