I have one thing I'd like to say. If you want to skill Sif, why not just farm Difficult?
Earth Page is the rare gold there
The team that I find works the best for Hell and Insane is a god team:
Sif Goddess of the Grain, Loki, Thor, Hel, Mermaid Queen (skilled) with helper Sif Goddess of the Grain.
You can use Freyja instead of Thor if you want to use a Dragon Knight instead of Mermaid Queen.
For a balance team, my one is:
Witch Queen, Sif Goddess of the Grain, Mafdet, Loki, Water Imp (Preferably skilled) with Helper Duke Shepherd Dog (Preferably skilled)
You can use Wicked Witch as a substitute and use the evolved form of Mafdet or Loki if you want.