Hello, I am not a veteran player, but I red a lot of articles with topic above. And anti-empire text is still missing, then I put this link, such a starting basis. author: Ovich http://splinterfaction.bigforumpro.com/t83-playing-against-the-empire-anti-empire-tactics Common hearing about strong and weak sides of Empire army. Other later.
I regularly face empire gunlines and I find that terradons and a JSoD or well geared FSoD do wonders at taking out their artillery, also consider having your slann take lore of metal to deal with those well armoured knights and the rest of the guns. As for their infantry, they are complete pushovers in comparison to Saurus IMO.
I find lore of light works better than light here, and I find that you should ALWAYS bring 2 units of chamos or skinks
Lord Tsunami: Of course its little bit older but I am thinking the basic mechanics of using of Empire army are described in this article well.
Salamanders should be effective against empire, lots of 20mm base infantry for maximum hits from the template or flame some knights and see how they like the -3 AS from the flames. I don't know what AS greatswords have, I assume its just heavy armour? Since GS are two handed. So they would be prime targets for a flaming.