First off, I’m glad he turned out to be a bruiser like I guessed.
Now if he doesn’t burst people on a regular basis (ignoring other potential ultimates) I think I’ll actually pick him up, cause he seems fun.
He will burst
His low cooldowns and his passive seem to imply that his pattern is meant to be spread out over a period of time, yes.
It is hard for melee AP to build sustained damage because Riot neglects them by offering no good build paths/ items. Melee AP sustain needs health, cooldown reduction, AP, penetration, and resistances and that is hard to build effectively pre 6 items.
Now let’s change his ult so it’s not mimicking everyone else’s ults
you seem 5 years behind mages and assassins do consistent burst now.
From my PBE experience, he does Burst pretty hard, though he can go bruiser deoending on the enemie team and thier ults. But mostly, he seems pretty broken either way because he can go ap heavy and has a solid base kit so he can abuse strong ults with no draw back. Malphite for example pays for the strong ult with a medicore base kit that doesn't work to well with AP. Sylias can easily afford AP heavy builts and with a malph ult he WILL explode the backline as he can follow up on it with a strong combo him self while also haveing aditional mobillity to get in range for a good ult.
Even if he himself is the paragon of consistent damage and 0 burst (something that's rarer these days among the new champ), but it still doesn't mean the ulti he stole wouldn't be a burst.
His ulti is basically a minefield waiting for victims (the opponent) to stumble upon it.
The fact that he's melee for one is what puts me in the hopeful camp that he goes that way.
He won't. I want AP bruiser to be his optimal build but there's no reason to go that route.
The 2 champs that still fulfill the ap bruiser role in the game rn are 
& 
the one thing they have in common is that they can abuse the shit outta 
. Their kit allows for the combo to work to it's fullest extent, something Sylas won't be able to do.
there's a few others who can roll with it but they often lack the melee requirement or they're more of an offtank than a real bruiser like karthus or amumu.
Sylas' core item is most likely gonna be a sheen item, as he's ap scaling 
seems like the obvious choice. after that he'll prolly go full ap burst to just deal with the current meta. 
is something that might help his bruiser build by giving him even more sustain, but it's not like burst champs don't like the item.
then there's the fact that he steals ults. If i were up against a singed i'd never even consider buying a tank item, i'd just steal his ult and go to town on his carries.
I've tried ap bruiser ekko, blitz, amumu and even mundo and none of them would be able to compete in effectiveness compared to the way chad singed and virgin(full tank) singed can compete with each other.
