AP vs AD (itemization flaws)

Just played a game where I was Veigar. The enemy team had an adc Vayne. The 2 of us were the only relevant damage source in our teams. It was a 35min game. So I had about 1400 AP. My ADC and the enemy brand were both underfed and barely useful in teamfights. So it was pretty much about who could carry - Vayne or Me (Veigar)

Vayne made Maw AND QSS to prevent getting cc'ed and one shot. I had to make Void staff AND Liandry's as the enemy team just stacked MR. In this game- I got a penta and a quadra (got ks'ed). I was farming like a BEAST. stacking my ap. and obviously losing a game when you're carrying so hard that your back hurts makes you tilt and salty.BUT! this game really did highlight some serious flaws in itemizations

AP items vs AD items Before going in a little deeper, a little stats about the game-

1. Our team did more dmg to champions. Both Vayne and Me (veigar) did about 50-55% of the team's total dmg to champions
2. Their team took way more damage
3. Veigar did 65K dmg to champs, Vayne 50K
4. Brand and Lucian both did 22K
5. Our team stacked Armor, their team stacked on MR
6. In the last teamfight, I did way more damage than vayne but we got aced they had 3 remaining

It is so much harder to solo carry as AP mage than it is to solo carry as the ADC. Yes, I know, vayne's a tankbuster has a %health true dmg. yada yada yada. And yes she's "supposed" to bust my frontline better than I burst theirs. But then again, I wasn't any normal AP caster. I was a 1400 AP veigar with void staff and liandry's. But the enemy Vi took almost 3 full spell rotations (without ult) to kill in the last tf. Especially annoying cause that stupid banshee's and Sterak's popped. Our Gnar with Randuin, deadman's, and thornmail was shred in a few seconds.

Here's what annoyed me so hard in the last teamfight, I tried to stun Vayne but she QSS'ed and ulted away. I flashed Q and R, usually this would be enough, BUT, Maw popped. and she tumbled away and went to lifesteal off of some minions. Now, me...to bust tanks and to penetrate some MR, had to get both Void Staff and Liandry's. And vayne doesn't need to get any armor shred. Yes Yes, I get it "% health true dmg", "silver bolts". But my point is this is a similar problem with ALMOST, (emphasis on almost) all the mages and ADCs. AD items are so much better. Armor pen can shred both tanks and squishies alike, same goes with Crit. but AP itemization plain sucks against MR stacking.

For reference match history-

http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/2278428364/210813558?tab=overview