Our problem is that Succubus has 2 charges of Heal (that's 20HP restored) and Solstice has Legacy, which gives him double defence, and restores all his HP, so theoretically, we would have to wade through 136 damage in order to kill Solstice. Killing Succubus early would remove all her spells, including heal, resurrect and hypno, which could instantly kill either Sam or Araches/Leetsan by moving them close to the hydras, and those are our two most important spell casters.

Killing Succubus would not only mean instantly reducing 20HP worth of healing, it means we can also move our units more safely. Any damage done to Solstice will be wasted once he uses Legacy, so that is why we saved him till last in the 3rd battle.

I think we could provoke Solstice to use Legacy by attacking him with either physically, or with a spell, so we can hurry up and use Randomtackle Manashackle on him.