Let me make something clear here......onymoudon, according to tobirama, is said to cancel all ninjutsu and right now, d only rhing capable of canceling it is senjutsu. What this means is not that the only thing that has effect on obito is senjutsu.....it directly means that the only form of ninjutsu dat can hurt obito is senjutsu....they dare not go against him in hand to hand combat(proof is using bm to attack and ward off incoming attacks) so their only option is using ninjutsu which is nullified except when imbued with senjutsu chakra. As far as I can remember, tobirama in all cases he talked about the onymoudon emphasised on ninjutsu and not jutsu of any sort so, jutsus like eight gate's hirodura, asakujaku and heavy attack which are not just ninjutsu would work on him.