I just had another playthrough specifically to test the githianky fight. And reach level 5. I reached this level without going into the Underdark, without killing the big spider, without killing the githianky patrol, and killed only 2 groups of goblins at their camp. But I completed everything else the main zone has to offer. (No, I didn't kill any tieflings, just followed the normal course of the story)
Considering this and if we leave no stone unturned, as an estimation, when we enter Act II we will have around level 6.5-7
