Ereb, choosing Sylvan as your faction is a good choice. However, you're making a big mistake with your hero selection; trust my experience playing as and against Sylvan (though you don't have to believe me; you'll figure it out yourself when you play against strong opponents). This faction is only competitive with Winghelm, and not with any other hero – that's a fact! The main point of his tactic is the initial strike with six units at the beginning of the battle; this is what determines the success of the endgame (I'm talking about the late game against any faction). Of course, proper development is also necessary; if you want, I can write it down for you in a private message?
P.S. Unicorns are good – as long as they're alive. But seriously, they aren't the key units for Sylvan; in my opinion, archers and dragons with Ents are better suited for that role.