That's a nice list of things.

I'll start by directing you to this site, which is a lot more active in all things Warmaster than here.

Next- Warmaster is very dependant on terrain. If you have a lot of terrain (primarily villages and forests) then it's best to take a mixed army. This is, in my opinion, the best way to play the game. If you don't have much terrain Cavalry (particularly things like you Empire Knights) are very strong.

Empire can have a lot of powerful shooting and their wizard lore isn't spectacular. It may be worth taking a wizard or two as back-up order issuers (or if you just like magic), but it's best not to take too many (unlike with some armies). Empire Heroes on the other hand are fairly important. Empire Ld is decent, but not excellent, so it's good to have a back up. A Griffon can be very nice, and is best for a Hero. Throw him into combat whenever you're confident you're unlikely to lose him. Never put the General on a monster, as he should be avoiding combat.

Don't try to rely on shooting alone- no matter how much you have it will need some protection. Steam Tanks are also not the greatest. They can be fun, but they're a support unit- not to be played as monsters.

I haven't yet had a chance to try out Empire for myself, but this is an example 2000pt list I'm painting towards:

1 General
2 Heroes
2 Wizards
6 Halberdiers
4 Crossbowmen
2 Handgunners
2 Flagellants
2 Pistoliers
4 Knights
1 Cannon
1 Hellblaster

(1980 pts)

I purposefully themed this army to be black-powder light, with a strong infantry component.

Hope this helps give you ideas. The people in the other forum I linked above will be much more knowledgeable than me on Empire though.