When the inevitable Sylas nerfs come...
For the record I have never before played a new champion before their first set of nerfs because I don't get any joy out of OP easy winning. With Sylas I made an exception becuase of the several ways he is unique.
When they nerf him I am really hoping they touch the heals and shield numbers as little as possible and instead hit his total dmg output while making the empowered W heal and damage have more demanding requirements then the %HP of him and his target. The reason I wish for this is because there is more then enough AP burst melees in the game and I don't want to see Sylas become just another one. His shield, heal, and passive make him uniquely adept to be an AP bruiser building some high AP components early and then tanky items later on to make the most of these throughout the game. I am worried about the capability being lost on him.
What they could do for the W: Add level scaling to the empowered heal and dmg so he cant over power melees in lane so easily, taking it down to 10% more at level one and bringing it up to 100% more(10% a level) by level 10 where it would be capped. Then roaming starts becoming more frequent and people have had time to build the grevious wounds passive but sylas can utilize it in the middle of team fights where it would be less of an issue since somone ought to have grevious wounds passive for such and he can be focused easily at the range he fights. A new stipulation should be added to get the empowered heal and damage at all so its not a super easy nigh unavoidable point and click vs every melee that trys to fight him(and nearly all others cause come on... his gap closeing). He should need to get three marks of his passive on a target before he can get the bigger heal and dmg for a short duration after. So he would need to Q,aa,E,aa,E,aa then W for the big heal and dmg. This way one can hypothetically get out of his W range while his E is down and avoid it lest the Sylas can find a way like flashing or if his Q CD is low enough he can slow you to get it. Say after about 2 or 3 seconds the marks dissapear and you can trade or finish your all in. With a coordinated team layering cc or each dodgeing an empowered auto avoiding the empowered W would be way easier.
Just know I adore this champion and would hate to see him become yet another burst AP melee that does tons of dmg really early hits 6 and you are dead, that would be so lame.
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For high AP enemy team:
For high AD enemy team:
comet, nullifying orb, transcendence, gathering storm, conditioning, and revitalize. 1-10% cdr, 9 AP, 15-90 hp.
that hurts your passive, Q, and E by a lot mitigating 200+ dmg beyond the magic resist it has thanks to its passive per spell rotation.
instead and sometimes if wanting to be more tanky throwing in 
Might also try a
as a replacement item, not sure.