You ready for this? I'm gonna drop some knowledge on ya. Let's say that you get caught out of position against Cho, and he manages to land his full combo on you - Rupture, Silence, Ultimate. Let's say this is end game. He has a RoA and Abyssal so he has 150 AP.
Rupture: 305 base + 150 ap (1:1 ratio) = 455 damage
Feral Scream: 275 + 150 ap (0.75 ap) = ~388 damage
Ult: 650 + 150( .7 ap) = 755 True Damage
So his magic damage is 842.5. IF you have base 30 MR - 20 MR for abyssal then you have 10 MR so you take ~90% damage. 842.5 * .9 = 758.25
758 + 755 = 1513 damage
You're saying that Cho'Gath can 100-0 you from full HP with this build by late game. You know who Cho'Gath can 100-0 with those items at level 18?
No one.
Mini-Gnar has the lowest lvl 18 health at 1645 and even he would survive. And even then this is assuming you don't build any MR or health at all, in which case you deserve to die anyway.
AND this is considering that Cho Gath has above-average burst damage for a tank due to his scaling and his ultimate dealing true damage. So this simply isn't true as far as the League of Tanks goes.