let's asume generalistic base stats: 2100health and 100armor vs 105ad, 0.650 base-as and 1.100AS at 18(estimated values that reflect the average basestats + runes of tanks/adc)
As items for the tank, we asume
(highest winrate built for Shen on champion.gg)
As items for the adc, we asume
(highest winrate built for Cait on champion.gg)
This results in 4100hp and 295armor(~200 bonus armor) for the tank, and 285ad; 1.750AS; 80%crit; 150%crit damage; 15 on-hit; 40% bonus-arpen and 15% increased damage for the adc
Meaning an effective 4100health+215armor so 12915 effective hp (hp x (1+armor/100)) vs physic damage for the tank,
and 1292 raw dps for the carry. (((ad x as x (1 + crit x critdamage)) + (on-hit x as)) x other multiplyers)
So in average, a single ADC at fullbuilt needs ~10sec to kill a tank with AAs.
Keep in mind that this does not involve any abillitys health reg, masteries or other buffs, nor the damage proc from RFC, as that is hard to asses in dps.
Every buff from monsters increases damage, but non gives tankiness, Materies give far more damage than tankiness, and in reallty a tank rarly **only **takes damage from the adc
So with masteries and eventual neutral bnuffs, it is probably closer to 8-9sec...
considering that this is only the damage from one out of 5 champs hitting the full tank with nothing but AAs and no steroid, i would say tankinesses looses, especially if we asume one of the other champs has some aditional armor shred.
However, at like boots+2-3 items, that would probably look rather different, as AA dps has many multipliers but low base values and outscales all and everything later on, while most tanky champs have high base stats and tank items are usually rather gold efficient in their effective hp vs a specific damage type.
If the tank was to fully buy 5 armor/health items, it would look differnt, just that he would die rather fast to any mage.
Mages usually have way less raw dps than adc, so they don't outscale tanks that much, though tanks usually are forced to invest far more into armor than into MR due to the huge raw damage of adc, and have less base mr.