Well, first off, try using Jack's Evade, as an Evade instead of a Quick buff? GGoR strips buffs, but it deals damage before the dispel happens, so Evade and Invuln both shield the entire attack.
Also, try using a blink Taunter. As long as Right Arm doesn't nuke them, you can bring in Saint George, Leonidas, d'Eon, or Mash to intercept the NP with their taunts. Even Emiya (Assassin) can force a Taunt onto someone else with a blocker.
d'Eon (though you're unlikely to use them because Jack is obviously your support) can use their three-turn taunt to tank Left Arm's NP, then Ibaraki's NP next turn; they'll even survive if you use their Evade to block Left Arm, then use a Mystic Code block to tank Ibaraki.
I know I talked about how quickly we were wiping Ibaraki earlier, but yesterday's raid got to 50 minutes left. I don't know how much dev assistance we're getting right now, but this may not bode well.