Veigar gets 140+ MR items and still he deals 900+ dam...help

I play LB quite a lot because her kits are very fun-and I like fooling enemies with her passive-and I actually do quite great, well, for silver 3.

Yesterday I was ahead of my game because I got 3 early kills from Veigar, then he started to get abyssal scepter. Then I rushed void staff, and with 35 flat MP and 39% percent MP(from mastery, rune and items), everything seemed ok.

However, things started to go wrong as our tryn wanted to go full AD with almost no MR/AR item, fed garen. We lost two top towers too early, and had to try to push top lane(their top turrets were STILL not taken down, and tryn is supposed to be good at split pushing) AND protect mid and bot lane, which was difficult as hell because our ADC wasn't good at poking and tryn basically was "VEIGAR PLEASE E AND R ME". Yeah he was that bad at dodging the stuns and snares from Morgana and Veigar.

Around 30 minutes mark, I realized veigar had 140 MR with around 400 AP(he had abyssal, banshee, morello, tome and Needlessly large Rod, which added to 260 AP), then I started to panic a bit because one, the banshee would negate my Q completely and too, I couldn't kill him with full combo due to high MR(the "true" MR is around 65 after applying MP) and he had 500 extra HP from Banshee. He Q and R me, then boom, grey screen(total did 2000 damage and my full health was around 1800 WITH scaling health runes).

So...yeah we lost. He got back in pace because we got distracted and lost. I was really bummed out because I usually did well even in late game(again, maybe because I m in silver rank), but lost this time.

What could I have done? I know it's not my sole responsibility to carry-its a team game after all, but I couldn't stop veig from farming after lane phase because the entire enemy team babysitted around me, and my team somehow didn't focus on veig, and it's needless to say how our top was doing.

Do you think I should have gotten health items like RoA? or rush Zhonya to negate Veig's ult? Maybe I should have told my team not to let veigar farm? I never thought veig would get banshee because I rarely saw one doing it. I mean I was only 20 CS behind him at the end of game

I could have gotten MR item like Abyssal item, but I noticed getting MR items significantly reduces her damage output...which is why I strictly stick to Void staff, Sorc shoes, Morello, Zhonya, Rabadon, and Haunting Guise/Lich Bane.

Please help me this noob silver, thanks.