Orochi's level of divinity has already been established. He is the god of nature, of earth. He serves to control the power of the earth and sees human as a threat to earth.
Well, just to say, Orochi's power is earth itself, so a rock or a lava or anything from earth will do nothing to him.
Also, people seem to misunderstand what happened to KOF 97. That time, Orochi was severely premature. Orochi then starts fighting them off . Everything, everywhere was destroyed. After a very decisive fight, Kyo, Iori and Chizuru was almost all out of power and Orochi was still standing unscathed, much to their surprised. They all starting to lose hope. That was when Orochi suddenly mocked them of their useless effort as Iori goes ROTB. It was then that instead of attacking the 2, Iori, suddenly grab Orochi. Orochi, unable to move, allowed Kyo and Chizuru to seal him. They all lost consciousness afterwards with Kyo missing in the aftermath.
What does this have to prove? First of all, Orochi wasn't beaten on all bruises and wounded like how people try to view a normal fight. By the end of the battle, Orochi remains scathed and the 3 almost dying in the fight. That proves a lot for a prematurely appearing God. Second, Orochi wasn't beaten by a simple attack. If you're fully aware of what happened in the past, the sealing of Orochi happen in a ceremonial fashion, the rest of yasakani clan use their power to hold orochi in place, while the kusanagi clan applied their powers to it and yata using their power to seal him off, which all cost the 3 clans to almost meet their demise.
The KOF 97 battle re-enacted the ritual. ROTB Iori used the power to hold Orochi in place, Kyo applied his power to it(in a form of a devastating flaming punch) and Chizuru sealed Orochi off. The point is that, unlike what people think it is, Orochi WAS NOT defeated in an "all-brawl" fashion. In the end of the very devastating fight, it was only the 3 scared treasures that can defeat an "unscathed" Orochi. Proving how he took on all those fighters on a very long fight while still far from his true power, yet still stand up and on top of that, unscratched, is a large proof of his power.
The use of Chris is because he is still premature. However, despite that fighting off all those fighters, he was unscratched, while keeping in mind how strong they are. I don't see how Akuma will deal a blow to even scratch Orochi.
Akuma fight's in a brawl fashion(destroy this, destroy that), which in any case isn't what it takes to defeat a god like Orochi. On the other hand, Orochi can just take all their souls and destroy them all together. Then it'll be over...