Syndra is in a bit of a bad spot right now. She can be rather strong, her Q damage is rather consistent, but her overall damage is inconsistent, which makes her a bad pick over someone else for mid.
She's rather like Cass with a spamming of her Q, I highly recommend smartcast, but because Q lacks a significant area of effect, it takes time for the sphere to 'materialize and detonate', it makes it extremely easy to dodge. Also, because of her playstyle, while lacking Cass's Deadly Cadence, I feel a ToG/Early Athene's is a must.
Her W, for the picking up of spheres and minions, is good, I find this to be an overall good ability, Especially considering the range is has, which can allow you to harass without worry of being blasted back, and the fact that you can cast it while moving. However, I feel the tether time is to low, and the minion/sphere itself doesn't move as fast when thrown, and the Cool Down is rather high.
Maybe make it so that every time she casts Q, the cooldown is lowered on W, that way spamming Q is rewarded or something.
Her E, I love for it's knockback, and while I feel the stun is also good, the aiming with it is a bit wonky. While I love the fact that I can 'curve the shot'. Sometimes, I feel as if I've hit the sphere head on, and it still curves off in a direction I didn't intend it to go, and I miss my target.
A stacking damage of multiple spheres hitting a target, would also be nice, and you could make it so that champions take 25% reduced damage after the first. I would like this, because if I've blown up my enemy with my Q and Ulti, there are so many spheres around, that an effect like that would have some potential.
Her ultimate, is also something I have a problem with, and in this regard, she's like Swain, at least from the way I've understood it. It's a number of shots, over and over, each hitting for it's individual damage, which when MR is built, lessens it's overall power considerably, because for all intents and purposes, it is a DoT.
When you are on the lower end of the sphere count and you fire it, it deals overall, less damage than a singular chunk ultimate, but when you're on the higher end of the sphere count, it has the potential to do more. There's only one problem though, Sphere's do not last long enough.
She's given a base amount of 3 Spheres, with max cdr, I can probably get out an additional 3, maybe a 4th if I'm very lucky. The reason why I want her spheres to last longer, is purely for the ultimate. Finding something to grab with your W is not a problem, conjuring a sphere with Q is not a problem, but to be honest, I want her Ultimate to feel like a threat.
In a team fight, to build up my ultimate to it's 'killing/threatening potential', I have to fire off multiple spheres, and then find someone with her ulti's semi-low range while the spheres last.
Meanwhile, most other APCs have no problem clicking R rather quickly, and getting their ultis full potential on demand, with exception to Cass or Brand.
Mostly, these are my complaints about Syndra, and what I would like to see happen to her, if I'm wrong on anything damage calculation wise for her ultimate or something else, just tell me.