Here is another solution somebody told me elsewhere:
1. You don't want to waste your resource to destroy the turret.
2. what you want is to get into the base of the tower, if you pay attention to the terrain surrounding the tower you'll see a subtle passage that allows you to jump down to the base of the tower.
3. You need 1 character with good lockpicking skills and 1 feather fall potions.
4. If you managed to go to the "back yard" of the tower, pick the glowing flower.
5. get in to the building via locked door.
6. solve the "puzzle" to turn on the tower "electricity" + deactivating the turrets.
