Thank you, Wikey. I've never built a Tear on Veigar, though I understand the appeal; the late-game Archangel's is kind of appealing for the nice chunk of AP you'll get, but you prolong your offensive capabilities (DFG or Deathcap). If I had to build something that wasn't Kage's or NLR early on, it'd probably be a Catalyst. I think they surrendered because they had no real focus. For example, Kog and Leona get caught out of position, and so Kennen and friends decide to take him down. Kennen pops his ult, I W him in place and kill him, saving us from AoE damage. Amumu runs around doing whatever, ulting and crying. Veigar tries to combo Kog, probably succeeds. Tristana also guns Kog down. But they very rarely went after me, much to my confusion. So I dealt massive damage to their team, and they were easily picked off. That could've been remedied by focusing me, but they were probably in the "we lost, gg" mentality.
Username, you shouldn't need Clarity on any champ. Veigar's passive helps out with mana management, but he also builds DFG to help his single target burst. DFG provides mana regen as well, so Clarity becomes pointless. The thing about that spell is that it's unnecessary early game if you just don't spam spells all the time, is moot early-to-mid because your jungler should be giving you blue buff, and late game it's useless because mana isn't an issue late game. It's arguably the worst summoner spell in existence.