I dont mind having a useless arcane (for pvp) as long as the mage arcane isnt too OP. Let me give explanation as I will get flamed by the frog community.

The rogue with full mythic will have around 330-350 dmg on L36. The mage with full mythic will have around 370-390 dmg next expansion. The buffed rogue arcane gives probably 300 dmg on L36. The mage arcane staff (yes itll be a staff/rod) will be expected to hit 700dps, around 350-380+ damage.

If a staff has any higher than 380+ dmg (even as an arcane) I would declare it as OP because its a DPS weapon not a damage inflicter - just like the arcane weapon for rogue.

My $0.02