For me the Gith fight has to be fought from dialog, as that's how the game flows. I find it difficult to win with lvl 4 and difficult to lose with lvl 5, no matter in what party composition. I never lost the fight with lvl 5, but the combats differ quite a lot. In one breeze-like fight I had no deaths in my party and many spellslots still available on my three casters, in one fight my last survivor in the party, my Light domain Cleric main, with 10 hp left killed the last Gith with his bow while running away because all spellslots were empty. In the last fight mentioned I used three fireballs and all hit only one of the Giths each with full damage. It's some randomness involved, as it should be.
So, my main advice is, be lvl 5.
