I agree, but with Rylai's it gives Veigar another escape option, which he does kinda need since his Event Horizon's cd is so long. 16 seconds at level 18 is life or death. And with Veigar's nuking potential and majai's, the dps carries are likely to try and run through your teammates or flank to focus you. Jsut saying that the 500 health could help in keeping your stacks. I will augment my build order and get the Tear before majai's, but still start out with the tome. You are right about ignite, but i like it for those early game kills(help you build up Majai's).

Overall nice build. My only suggestions would be to rush the Archangle's Staff first, or at least the tear. My reasoning? Baleful Strike, if used to last hit minions, rewards you with AP. If you rush Mejai's, you wont have that extra mana regen nor the ever-increasing mana pool with each spell.

Secondly, I can see how getting Rylai's is a good idea for survivability, I hardly ever get it. I do buy it in place of my Mejai's if I keep getting focused down and cant keep a steady amount of stacks. I would also recommend that if you can keep a good amount of stacks, skip the Rylai's and buy a Void Staff. Veigar should never be in harms range and always behind his team in team fights so the extra health and slows from Rylai's doesn't really help much whereas the extra penetration from Void Staff does.

As for the summoner spells, I usually go with Teleport and Exhaust. Exhaust saves you from melee champs if, and when, your stun is down and teleport allows you to jump around the map getting either assists or ganks to further build your Mejai's. I can see, however, that Ghost could be beneficial. As for Ignite, you do so much nuking at the end of the game, with your spell rotation you wouldn't have time to put up ignite.

Those are my thoughts. :D