Heimerdinger and Rylai's

Do Heimerdinger's turrets proc Rylai's or Liandry's?

Yes, because Heimerdinger's turrets are spell damage, which procs Liandry's, which will cause Rylai's to be proced as well.

Addtionally, does anyone know of any counters to syndra mid?

Any bursty champion with point and click cc usually gives Syndra a hard time. One of the most well-known counters for Syndra in the LCS is Ekko mid.

Yes, Rylais works.

Honestly, if you can survive Syndra's early game so you can scale with her into the late game you'll be ok. Champions like Orianna, Ahri, Cassio, Ziggs, Xerath, Lux, Viktor, AP Kog, can put out just as much if not more damage for teamfights to come out in better shape. Barrier is also a good summoner to take vs her to survive her lvl 6-10 all in. She excels in single target burst with her ult, so once she hits lvl 6 she will be looking to all in you. Pay attention to her orb count and when she starts getting a lot out try to back up until they go away, as they will consume her mana early and mid if shes trying to stack up a huge ult count.

Around level 5, if you're around 55% or less, pay attention to her mana, if she has enough for her entire combo once she hits 6 you will die. picking up a minion with her W to slow you for a free QE into a R will kill you. I find some match ups vs her if I come out ahead in CS at 0-0 I can generally do more then her as the teams start coming together, In lane as Syn I feel I hate playing vs the long range mages that I have to walk into them to hit them with my decent range.suck the most to deal with. (Example) Ziggs can just EQ you as you try to start you're Syn combo and then you're slow and taking a good portion of you're HP to try and hit a long range Scatter the Weak (E) that he can pretty easily dodge or still be far enough you have to keep moving through his mines and by the time you get to him he can now QR and barrier you're initial all in combo. Orianna is also a pain as she can deal a good amount of damage while shielding herself as well.

I've played a lot of Syndra (most of it before Champ Mastery, she was my go to champion season 4/5. I'm more obsessed with getting other champions up to lvl 5/6/7 I don't play her as much as I used to, but I play a lot of mid and I've found that trying to counter her isn't always the best move. sometimes it's better to just pick someone who can survive and fights better in teamfights, not allowing her to roam or snowball will basically keep you on even terms going into the mid game so it then comes down to if you can just do more then her. Of coruse if you're better then her you can still tip any lane in you're favor so you try to snowball lol, as with any lane/position.

Ty all, that helps my build a ton, making it a tons more cancerous