To a certain extent I agree with both darkrai147 and runbabyrun but I think it all depends on why the Pokemon is being suspected. If the Pokemon is just so much of a problem that it destroys certain types on its own no matter what its teammates are (ex: Talonflame) then what type it's on shouldn't matter in the slightest. If the Pokemon's viability or brokenness is heavily dependant on the support it receives from its teammates (ex: Mega Gallade) then of course the typing should be considered when deciding if the Pokemon needs a ban. So we need to make a decision with M-Altaria. Is it so good on its own that its teammates wouldn't matter? Or is it possibly broken just because it has good support?
In my opinion, Altaria is a special case in which it's a little of both, but Dragon and Flying have enough support that I think it should be banned no matter which of my descriptions fit it better.
As a side note, Monotype is probably never going to be an official tier. We may be the most popular OM, but aspiring to more than that is probably a lost cause. And to be perfectly honest, I'm ok with that.
In my opinion, Altaria is a special case in which it's a little of both, but Dragon and Flying have enough support that I think it should be banned no matter which of my descriptions fit it better.
If Monotype wants to become closer to an official metagame, then the focus needs to be on Altaria.
As a side note, Monotype is probably never going to be an official tier. We may be the most popular OM, but aspiring to more than that is probably a lost cause. And to be perfectly honest, I'm ok with that.