Stacking is one of the most important aspects of this game. However despite what many tell you there is no one good stack. On any given day any stack can beat another.
With that said there is better stacks for eavh color while not perfevt can be very sucessful.
The issue of land grab has a lot to do with fodder stacks.
Fodder stacks are mass stacks of lower power units.
Example zombies Sprites dryads ect
When these mass lower units are combined with your stack and you win the battle you of coarse win more land.