Does Wielder of Water get +2 might if an opponent uses Fight or Flight to remove the other defending unit, leaving Wielder defending alone?

Ruling: Yes, Wielder of Water gets the +2 might because "while I defend alone" is a passive ability that continuously checks the game state, so it applies when Fight or Flight resolves and Wielder becomes the sole defender.

Nuances:

• A "when I'm defending" trigger would work differently - it would trigger during the initial defend chain or when the unit joins combat mid-combat (added in CR 1.1)
• "When I'm defending" triggers can only happen once per unit per combat, even if moved in and out repeatedly
• The +2 might from Wielder's passive ability is not a "buff" in the game-mechanical sense (not a Buff game object)