1) Creatures can already attack their master.
2) Creatures can already consume others.
3) An aura is a new type of effect even though the +2|+2 is not new
4) "Every turn a random enemy creature is infected"
"0: Toxic Gas: A random enemy creature is infected"
The basic effect does not differ...
1) False; there is currently no creature in this game that attacks its master
directly and
without any support from other cards. Psions and SoW Immortals attack their master if they encounter an Emerald Shield, but this require a combo to be achieved. Liquid Shadow & Antimatter on a creature makes it to attack its master and heal its opponent, but still requires a combo. Keep also in mind that your shield affects Orochi if it attacks you.
2) True; however, the devouring mechanic of Otyugh and Scarabs increase their hp by 1 for every consumed creature, while Orochi stats remain unchanged. However, sacrificial effects similar to Orochi's exist via Immolation or Virus|Retrovirus, that sacrifices itself to poison enemy creatures.
3) I totally agree here, but for me it doesn't really interest me a buffing aura as a new kind of effect.
4) The basic effect does not differ, however in the second case it is likely an active ability which can be lobotomised, while in the first case it seems like a passive ability and can't be lobotomised. So, I agree here with you of different implementation, but as I said above, I just don't find the buffing aura interesting enough to vote for it...