People saying that there is not much they can do to differiense ARC with MSK in my mind they are wrong. ARC is a no combo range attacker with piercing dmn while MSK they could make it a combo oriented range blunt dmg that could benefit for MNK Dragon Kick debuff. They can have some debuff to lower target defence/mag. defence and a bunch of stuff. We know that the animations been there since 1.0 and within the NPC.
