Yeah, Rin wouldn't get more than one or two effective shots off even if she blew all her jewels on it, and it'd have to be at close range to pierce the crazy boosted defenses. Caster's beamspam array could have worked though/
Archer is wounded in Heaven's Feel, so he won't be able to take her on at peak. Unlimited Blade Works takes too long to cast against an enemy this fast, and the muck won't let him either. Maybe he can Project and fire Gae Bolg from a bow?
Gilgamesh might be worth a shot, but against Assassin, Alter Saber and Black Berserker...well, I doubt he'd last long, even for the King of Heroes. Unless he opens the fight with Ea.