It's pretty difficult to go wrong with blunt and fire, so yeah, staff of embers is the king... It's ranged, large AoE, can stagger enemies, has very high damage per action length, and doesn't require ammunition. Elemental staves in general are perfectly usable with just one meal of eitr, and don't require stamina for casting. There's nothing in the game that staff of embers is ineffective against. Its only weakness is low durability.