A lot of ppl around here will recommend PB's for Grief because:
1) All PB's are indestructible (good for Frenziers!)
2) Grief doesn't add %Edmg, it adds 340-400 (depending on your roll) straight dmg. So, the low base dmg of PB's is small compared to +340-400 dmg.
3) No strength requirement, IIRC.
4) There isn't an axe that can match the speed/indestructibility on a PB.
GL!