I've been pvping darkness since early januari. I usually win at least 4 out of 5 games. You often get the upper hand quickly with this team.
I use Ghostly Skull
with my raven, and Feline Familiar
for backup Darkness
Unless there is magic spells in the enemy team I open with crow/raven. Skull is good at soaking damage and is good to throw against reflection pets (which are usually humanoid).
The success of this teams is much thanks to that many ppl PvP with dragonkin and humanoid.
Raven > Aquatic, Dragon
Skull > Humanoid, Flying
Cat > Critter, Dragon, Anything without one-shot counters.
Mechs is still pain.
Elementals might require planning.
Raven and Cat has low health, which is the teams main weakness. But Skull wear most of the enemy damage out.