MC and seelah have shake it off, their mounts have it too. I would expect they are constantly beside at the very least their mount, they are also typically right on top of each other attacking the same target. It never shows up in saves. Other characters who do not have mounts are also in melee and adjacent and it never shows up as part of the calculation in the combat log or in character sheet.
Did you check the actual final numbers? Calculations in the combat log may not always show the full formula.