I'd honestly expect you to be a bit more smarter since your plat 2 but, like every tank in the game he falls off. How to counter his passive?
into
, uhh
and also 
high damage early I'll admit, but without red buff his damage is only in his ult, how to counter his ult? Magic resist and also
with
will reduce his attack speed,
is really good to counter his early ganks.
anymore questions?
edit: gonna add more stuff that destroys him, a good
but very rare to find,
if you already have grievous wounds in your kit
can help spread grievous wounds during team fights without you focusing him from
or just pop ignite on him and he'll be useless,
slows, everything that slows
slows and destroys voli in 1v1s,
and everything that slows pretty much.
your gonna want someone that has %health damage which is probably the best thing that counters voli, with grievous wounds he's useless,
destroys voli with her passive
and
and can kite him and destroy him.
is really good on voli but if you got %health damage it punishes him for buying it too so you can out damage his heal as well with the attack speed and dmg from %health dmg.
im not sure if I said it but g r i e v o u s w o u n d s