I think they changed it so the idea was that mercs are for lower level players under the power of level 7+ troops, and from then on they are no longer required as you should be researching a broad strategy within your own race. This is how it seems to me anyway.
"Corn chips is no place for a mighty warrior"
Also Known as - Kenshin Himura
Rufio 54 - Crown Prince
Dragonroost 62 - Ex-Icarum King, Ex-Neferak King
Swanshire 102 - Skarn - House Ragnarok