A. There's a definitive lack of evidence proving that the item is too strong.
B. If you were destroying in team fights up to that point, then you did something WAY wrong, one item doesn't make that much of a difference, EVER.
C. No team should stay behind, smart play and careful actions can and should give you a window to turn the game around. Otherwise what would be the point?
As for the person that wants to say my point A is wrong.
100 armor means you have 100% effective health, double your effective health. This also means you're taking half damage from physical sources. Last Whisper ignores 35% of your armor. To still have 100 effective armor, that is 50% physical damage reduction, you only need 55 more armor. This is easily possible by any tank. At 310 you still have 200 effective armor, that is 300% effective health, I believe that comes out to 60-75% physical damage reduction.