I disagree with your reasonings on not getting Lichbane. Its easy enough to time your auto to hit right after your baleful strike. I do it all the time. And with late game, your baleful already hits a bunch but to fling 800 some AP directly after? That is close to a 1.5-2k~ burst of damage. Lichbane is definitely worth it.

Also, RoA is a good choice because it adds to survivability. Although your build seems it can nuke someone to hell, it doesn't give much survivability aside from Zhonya's. Also, I would go Boots of Sorcery because magic penetration is helpful.

IMO that has no sense, because:
-Zhonya's Ring is already here and it isn't expensive
- Lich Bane - Veigar's attack speed is too slow to hit, someone would run away before I combo him down
- Rod of Ages - Too low AP IMO
- Boots of swiftness are here, but if u want u can sell them and buy one more Archangel's Staff for more AP
- Deathfire Grasp - u want to one-shoot people with ulti or cast a combo like this:
Event Horizont-->Dark Matter + instantly Baleful Strike-->run when the victim may try to run-->Baleful Strike again. That person will remember you forever and he/she will hate you forever:)) U will not need Deathfire grasp for this.
If u wanna gank some people, then u will do MASSIVE damage to everyone who will be hit by your Dark Matter so you are extremely good for ganking.:)

... hey dude this is very expensive build..u mast have minimal 27 kills...try to add some cheaper items but with a lot of AP..for exemple : ZONYA S,LICH BANE,AH. STUFF,ROD OF AGES,DTHF GRASPH,BOOTS OF SWIFF...