Tactics for playing as the Sylvan faction.

Personally, I've always respected educated warriors, meaning warriors with education. Their strength is tied to physical damage, and extra stats in defense and attack will be very useful. And it's quite easy to increase education for Sylvan units.

Attack is a rare characteristic for Sylvan, so even if you get education, it won't give much. It's better to increase the damage of Sylvan units using Vengeance (the attack branch). + Mask of the Avenger helps a lot, and Luck, of course. It would be good if you find a couple of decent artifacts for attack (Moonblade, Dwarven Axe, etc.).
I don't always take education, because I'm sure that defense is more effective (of course, if your opponent is Dungeon, then education is better). Still, the main stats that Sylvan units often get are knowledge and defense. That is, if I'm going for an elf-chaos mage, I take education. If I'm going for an elf-warrior, I take defense.