yeah... the wario that i fight doesent even abuse bite, and he still beats me all the time.
but the one time that he did use bite, basicly the only counter that i found was to wait for the end window to punsh... but bite can beat out a lot of sonics attacks, and makes wario really hard to approach.
(but to be honest, vs bite.. i don't have enough experience to say... and I'm sure there are counters for it, but i didnt fight it long enough to discover them)
There are a lot of little things that make wario hard to fight... for example, wario's aerial approach is really hard to counter... its like that jiggly-esque jump forward, aerial, pull back out of range... repeat
there isnt much of a punish window on it, and he can keep doing it over and over.
warios Uair can actually beat out sonic's dair(which is a huge deal imo), and warios fsmash can come out of nowhere, and it has SA, and wario has a lot of moves that have killing potential... wario's main drawback i think is that some of his moves are punishable afterwards, and he has short range... but sonic suffers form the range thing, and has a harder time killing.. and sonic... has a lot of attacks that cause him post delay as well...
Its just hard, Wario's Fsmash makes him better than sonic at extreme close range, so you have to space him just right and time a fmash, or tilt him away... and in the air wario is a beast, so if he sees your attacks coming its really hard to beat him.
but at the same time... airials are the best way to fight wario... because sonic cant really approch him any other way.