Omega Red's Death Spores are not scaling at all with attack boosts/nodes
After a bit of testing, the damage from his death spores (both from signature ability and death field) do not scale with any attack boosts, masteries, or class advantage/disadvantage. This is stated no where in his spotlight. Passive degeneration has been shown to scale directly with attack modifiers before like with Dormammu's passive degen. This is hindering omega red's effectiveness by quite a bit.
As a side note, I've noticed another bug with him where death spores will continue to fall off when you're still within striking distance proximity of the opponent.