Very few ATs can have every resist maxed and few players of those ATs will have them maxed. They however will have little to no def resist and what defenses they do have will fold easily so more defense buffs will help them.
In reverse, the defense sets will not have maxed resists and may not have full DDR. They can be taken out by auto cheese hits so extra resist buffs will help.
For anti mob support, a lot of AVs and GMs will head for the hills as soon as someone drops a defuff on them, so stacks of immobilizes on them help. Enough control will work on AVs and GMs.
Though easily used on the move support is generally better in this modern day "We need to be done with the mission before we have fully loaded in mentality."