If she is 'balanced' then we praise Veigar as the GOD OF GODS!!!
His Burst is stronger than Syndras but people do not ragged on him as much simply because he does a horrible job protecting himself. Once his e is cool down, all in him, no issues. W may be big aoe (bigger than Syndras) but not hard to avoid if you pay attention to the shadow. But the same is true, if not even worse, for Syndra. Her only 'disengage' is her e, also on a long cool down. Unlike Veigars wall, which is a definite stun, Syndra must have a q e combo to stun, and the sphere must hit the target, otherwise it is just a know back. Meaning her 'disengage' is on cool down and chasing after her, assuming if gap closing is available, is an exposed Syndra. So Veigar's 'disengage' is better than Syndras, especially when he can use his wall as a zone, either you go around the wall, run into it, or back off. Why do people rag on Syndra more?
Another reason is because Veigar has a higher play rate and thus you see a huge range of him being trash to god tier. Syndra, however, does not have no where near as high of a play rate and so every time players see her, they see her as a threat and plays well. That and the mental mind set one has when they see Syndra, like when they see Yasuo. "Ah God! Yasuo. Time to have a filthy headache for this match" That is all in the mind set, though there are ranges of terrible to god tier Yasuos, they are clumbed up together. Even the bad Yasuos, if they managed to get a good wind wall, dodge skill shots with his dash, or get a few kills, are just as annoying as the great Yasup players.
Back to Syndra and Veigar, my point was, all Syndra players are placed in that group, like Yasuo.
Syndra's primary attack ability (q) has lower cool down (I may be wrong. I do not care to open wikia to see the cool down on their abilities at the moment. Give me a day) so she is a bit more forgiving for missing her aoe.
Veigar's stun is a wall where you must stop your auto pathing or else you are done for. Syndra does her q e combo, which while may seem like a less reaction time in dodging, Veigar has a much better team fight with his stun then Syndras. Not to mention, Syndra can miss her her stun. It is like hitting a ball with a bat, you have to aim your bat carefully, or else you will miss. It is positioning her, Syndra herself. It is not like a line skill shot. Veigar, as long he didn't click elsewhere on the screen, missing the stun is not possible (Sion ult, Morgana Black Shield, Banshee Veil not included). It is simply positioning.
Any other reasons why Veigar is more powerful or why Syndra gets ragged on? OH! Hey Veigar! How oftern have you had over 1000 AP? And you Syndra? Oh... That's disappointing. Hmm. Veigar has means of getting AP as part of his kit! Yet people ragged on Syndra, who is limited to items! ( and Runes and masteries)
Both have point in click spell ults. Syndra gets ragged more because... you visually see more spheres hitting on you, as such, equating each sphere with it's own individual damage. Unlike Veigar, who has just one projectile.
Anything else?
As far I can see, Veigar is more annoying with his burst. The few things Syndra does better is her q cool down (I will confirm this tomorrow. I do not want to open another tab tonight), her... ummm... I think that's it. Anything else I can say Veigar does better, yet no one rags on him. Nerf the low play rate Syndra and leave the higher play rate, more powerful Veigar alone.