He doesn't really need that many buffs to become a viable hero. His aghs is really good. The biggest things holding him back is the low movement speed of 290.

I think people often undervalue his spells. Like sure his lvl 4 Q is only 240damage, but if someone uses a single spell that's already up to 440, not to mention the damage over time + movement slow. The lvl 15 talent brings that up to 420 + 350, hard to resist the +2 int steal talent though. And maybe most importantly, it has a cast range of 1000 + an AoE of with radius of 425.

Aghs makes last word an AoE ability with a radius of 650 with a cast range of 900. What's Silencer's biggest weakness, relatively squishy/easy to kill. Well not if you're spamming your abilities outside the fight. Someone BKBs to remove the silence, that's what you have your BKB piercing ult for

​

He's not a broken hero by any means, but give him some movement speed, or make his Q slow more/increase base duration nerf penalty duration/give him some armor, it might be enough