You are running almost exactly the same list as myself, like almost literally the same list. It works really well however I think you should tweak a few things.
Drop the musicians on the empire knights. They are not fast cav so you wont be able to act as normal even if they do rally. They are your chaff units, you want them to be as cheap as possible so 110 pts and not worry if they get destroyed. Literally just pick some targets and throw these knights against them. Usually against enemy chaff
Or if you are going to flee then just do it. They are chaff so dont worry if they get caught.
The standard bearer on the demi's is a waste of points as is the musician. If you flee the standard bearer will die and that is a big model to lose and you have pretty high leadership anyway so the musician is usually a waste of points. As long as you pick your battles well you shouldnt need the muso.
If you are going to take a hellblaster then you need to take a master engineer with it. A master engineer is just too good not to take. He gives your hellblaster BS4 and allows you to re-roll one of your artillery dice which should allow you to get no misfires and have a devastating effect. Because we have to roll to hit now the BS increase is amazing. It makes the hellblaster go from a decent unit to a great unit as almost always you'll be at long range so it is already a -1 to hit.
You need a unit of archers to put your wizards in. They are skirmishers and provide ablative wounds. Also because the unit is skirmishing it allows you to move around easily and avoid combat as well as give you some extra protection against missile fire with that extra -1 to hit.
One thing to consider is giving your BSB an enchanted shield for an extra +1 to his armour save.
So all in all you have a really good list. If you were to change only one thing it would definitely be putting your wizards in a 10 man archer unit.
Good luck with this list. It has proved really effective for myself. Just keep your war altar out of combat and blast away with your magic and warmachines. Personally I would drop the cannon but thats just because of my experience. I am running an Ostermark army and my warmachine crew struggle with operating cannons. In the last 6 games I have had they have killed a single cold one chariot and 3 warriors of chaos and they misfired literally everygame
Contrary to that my archers have killed a chimera, 2 skull crushers and around 20 various infantry. So I hope your soldiers come from Nuln or Altdorf and know how to operate their warmachines
