[Insert Standard Disclaimer that there is no "strongest" anything.']
Having said that, IMO, the strongest team is Graves/MPD/X, for values of X in the set
{Ghastly Kid, Murkalot, Ruby Droplet, Alterac Brew Pup, Magical Crawdad}
I've beaten Murkalot/Graves at least three times in the last 700 matches, and never lost to it, so I don't particularly fear that one.
Without a Graves of my own, I have never got
close to having a vague possibility of thinking of imagining how to draw with Graves/MPD/healer or Consume Corpse Graves/MPD/Kid, played competently. Abandon all hope. I've met Consume Corpse Graves/MPD/Kid many times, and I haven't even scratched that - ever. Of course, it's likely that only experienced players will go for Consume Corpse Graves, and that's a big factor. I plough through Graves teams that are played by beginners, but when my opponent can guess what I'm going for and counter it, and has Graves/MPD/Kid, I'm dead.
Without Graves, and if looking for a beginner team that doesn't require skill, I'd go for any combo of Bone Serpent, Weeb, MPD ...
ma-aybe FoA. Three Weebs. Three Bone Serpents. Two Weebs and a Serpent. Three MPDs. MPD + Serpent + Weeb. I've run into several of those this week, and, honestly, that's what I'd recommend. If you have Graves to add to that, great!
My overall win rate usually goes 70%-80%. The last time I did numbers, my win rate against these combos was like 20%-30%.
That's what the game is at the moment. Those pets have a crazy advantage. Those are the teams that will win most of the time. If you want to win, use them.
If you do want to avoid that, the strongest team I know is Disco's Rich Girls. I never go twice into the queue with the same team, but I used it quite a bit in my sprint this week:
http://pvppetbattles.com/wod-teams/
H/H Bone Serpent (Bone Barrage, Call Darkness, Nocturnal Strike)
P/P Junglebeak (Peck, Rain Dance, Nocturnal Strike)
S/S Nightshade Sproutling (Lash, Call Darkness, Blinding Poison)
When grinding wins, it has the extra advantage of being fast and mitigating against healers.
Close contenders of the tricky variety:
Disco's Kid, Look What You Done Did
S/S Fiendish Imp (Burn, Immolation, Nether Gate)
H/H Ghastly Kid (Hoof, Ethereal, Haunt)
H/S Scalded Basilisk Hatchling (Crystal Prison, Feign Death, Thrash)
Vergilioar's Equilibrium
http://www.warcraftpets.com/community/forum/viewtopic.php?f=3&t=14409#p125900
S/S Fiendish Imp (Burn, Immolation, Nether Gate)
H/H Ghastly Kid (Hoof, Ethereal, Haunt)
S/S Nightshade Sproutling (Lash, Nature's Ward. Blinding Poison)
All three of these teams take quite a bit of concentration to play well, though, and I can say from experience can leave you burned out after a long session. I started the week having fun with Willy, got the idea of making the 1000 while the queue was popping quickly, and alternated these kinds of teams with no-brain The Evil Undead (feat. MPD) and I now don't want to see a PvP match again for ... quite a while.