anything that's not an
attack.
Therefore, FTG can completely bypass yata, so can kamui and Bansho tenin. Any genjutsu can bypass it seeing as it's less of an attack and more of using your senses(notice DB says astral, physical and ninjutsu; no mention of genjutsu). Gaara sand can also bypass it because gaara uses the sand inside susano'o to pull the user out, thus he has completely gone around it because yata is on susano'o and not itachi.
There are quite a few things that can
Bypass yata mirror, but nothing that can flat out defeat it. You have to Bypass yata, not destroy it. In any case, the fact that itachi has it on his susano'o and itachi has a sharingan elimates almost all jutsu that can actually bypass it. There's a reason itachi put it on his susano'o and not his jacket, because he knows that susano'o can guard him against jutsu that happen to bypass yata.
Dr. Proof has a theory that it only deflects one attack st a time...so on a basis of physics its theoretically possible to time two attacks to where it alters to deflect one, but is unable to block the other due to it being in the wrong form....it's all theoretical though which is why I out it second.
Nonsense seeing as it blocked multiple explosions from multiple tags along with 4/5 heads of hydra thus debunking any fallacy that multiple attacks can bring it down. when one tag would have blown up, there would have been another incoming, therefore yata would have been hit with physical (incoming kunai), explosivee and elemental(explosion) damage at the same time/short interval.