Another weapon you can give a commander that normally just stays in the back is the Rod of the Phoenix. It costs quite a bit more than the Sceptre, but has the spell Incinerate that has a 100 precision and can hit from anywhere on the battlefield it seems.
I haven't had a chance to try the Sceptre of Authority yet to see how they compare, but Last time I played Arco and had lots of extra fire gems lying around, I put the rods on my Strategos commanders whom I normally keep out of battle to use their standard bearer ability to keep troops fighting. Armed with the rods and quickness boots, they could do some real damage from long range that helped turn some battles for me. Once in a while they would even take out enemy commanders towards the beginning of the battles
. Also, the Incinerate spell on the rod would only take 5 fatigue per cast. I am not sure if that is normal or not, but it is a lot less than the spell of the same name.