I don't think Counter really deserves its own set. Counter is more of a gimmick since, although Blissey is good at baiting physical attacks, it's even better at baiting setup (e.g., Belly Drum). I'd make Counter an OO among the other moves that are illegal with Heal Bell.
I'm wrestling with the other 2 moveslots in the main set; I don't think there's really a "standard" set as far as those two moveslots are concerned. Generally, any combination of Toxic/Sing/Light Screen/Growl/Elemental Attacks works, with the basic rule that you shouldn't be doubling up on attacking moves (it is Blissey, after all). I wouldn't make Growl a main option, though. If I was to pick a standard moveset, it'd look something like this:
Blissey @ Leftovers (duh)
-Heal Bell (duh)
with Flamethrower, Toxic, Growl, Ice Beam, and Thunderbolt/Thunder being in OO or even in AC. Sing might be contestable as the "main" option, but really, what else is Blissey going to be accomplishing? Might as well try to sleep something with that fourth moveslot.
Again, though, this is hardly the only way to do things. For example, Flamethrower/Ice Beam + Toxic can work to keep Poison-immune things out of your hair (Flamethrower for Steels, Ice Beam for Nidoking), and Thunderbolt + Light Screen lets you support the team while preventing Cloyster from switching in willy-nilly to set up its Spikes. There's a lot of ways to mix and match these last two moveslots, although I should point out that it's not because Blissey has a lot of good options (the opposite is closer to the truth), but more because the other two moves don't really matter... which calls into question why I'd bother writing so much text trying to change them. Hm.