I have to agree here, triple ap IS an automatic loss without massive snowballing, double ap is already very dubious since 1 item can completely negate the damage of 2 people on your team.
MR is a massive hard counter to AP champions, unless they build full glass cannon, you don't have to worry about them doing damage to you. Not to mention their items are much more expensive.
Armor is not a massive hard counter to AD. AD's can consistently do damage without waiting for cooldowns, and ad items are much cheaper than AP.
The only reason a single ap mid is viable is because them wasting an item slot on you is a win. 1 ap vs 0 ap, the 1 ap team does not have to ever build MR while the 0 ap team might have to if the ap gets fed. (exception, ad auto champions that can massively deal magic damage)