You guys are going on about mu's invisibility as if he he can actually attack in that state. He needs to be visible to use dust release and as soon as he's visible, he'll be detected with sensing.
4 Kazekage doesn't blow either. Using gold dust to spread across the battlefield would help in locating Mu with the help of the third eye technique. Same way Gaara located Mizukage's invisible clam. If Mu is caught in a storm of gold dust then it will cover him with dust and make him visible. If Mu isn't detected by 4th Kazekage then it means Mu is probably flying out of range, meaning he's not in a dangerous or worrying enough position to attack them; so with gold dust there's no way he's sneaking up on anyone.
And whoever said Ay can avoid Tobirama because minato could needs to think again. He probably can a couple of times but not forever , Ay knows well enough how FTG works and Tobirama isn't using dozens of Kunai's. With Ay's v2, he'll try to catch Tobirama appearing to whatever marked kunai or object he teleports to. Besides, it'll take a lot of fire power to damage Ay, water style ain't gonna cut it, neither will a kunai. Only thing that will stop him from team second is dust release which will never hit while in v2.