No, burning of Teldrassil didn't happen because it was the plan, it happened because one dying elf said something to an undead crazy elf ("you can't kill hope" "OH, CAN'T I?"). It was an on the spot decision against the original plan. Instead of holding the city hostage and preventing Alliance from aggressive reaction she basically started the war which resulted in her losing her own city and many casualties. On both sides. Brilliant strategist, military genius, Sylvanas Windrunner, the famous defender of Quel'thalas who decided to slide right in front of the Lich King and basically kill herself. Twice.