Veigar !?!

I'm not even sure if this is a bug, but its something that even the enemy team was questioning. I was just playing veigar, Magic pen marks, Armor seals, Scaling ap glyphs, Ap quints. DAMAGE Okay, I had 190 q stacks, a Zhonya/Morello + a needlessly large rod - with sorcer boots. My ult was tier 2. It never did any dmg. Like of course, It would do dmg? Yet it never actually hurt. After game lobby we looked at my dmg dealt to champions and I had the lowest on our team next to the support. Even though I'd been in EVERY teamfight, and had ulted most of the enemy team a majority of the time. It was almost always on cooldown. It felt like all of my dmg was severely reduced, tooltips read 300dmg + 445 (Something like that at the point of the game where this ult would of / shoult of executed a low hp miss fortune.) Thats around 745 dmg, + 80% of targets ap right? Okay so if they have 0, thats fine. But It was doing more like 200 hp. She had the mr glyphs, I just checked. Yet she still took so little dmg.

Was something changed with Veigar? Normally by that point in the game I can one shot a carry, I was running thunderlords. I even pulled off the thunderlords auto q ult combo on her. She didn't die, She was below 500 hp. She didn't even die. She even said, "I should of died." Cause it was a suicide kill for me.

Could this be a bug?