Outdated? A bit. Mostly, his problem is that he got repeatedly beaten by a nerf bat for no good reason.
His fear got nerfed.
The Fear mechanic was changed to directly counteract the rest of his kit (fear them away while you want them to stay near you).
His E lost its chain silence.
His W lost a lot of it's tether range.
His passive got nerfed, so that he has to hit people rather than it being an aura.
Oh, and FUCKING RUNEGLAIVE.
Could he use changes? Yeah.
Something that could be a thing would be to turn drain into a Karma W style tether, where he can move, attack, and cast spells (excluding second drains, obviously) while draining.
Suddenly, Fiddle can build runeglaive, because his autos will not impact his ability to be a mosquito. A new build could come from this as well.
(sell runeglaive later for
)
Due to being able to waddle along while draining, this pretty much garuntees that whoever you latch onto will have a bad day, due to the constant slows and your heightened movement speed.