Tactics for playing as the Sylvan faction.

IMHO: 3 heroes per castle... if the game is "fast-paced" (in principle, the longer the game lasts and the larger the map, the more heroes there should be). 3 heroes can gather enough resources to develop the castle + the troops of these heroes + explore the territory (if you are playing on an unfamiliar map). If the hero is from the left castle (e.g., Dwarves), their troops will serve as excellent "cannon fodder" against mobs.