Githyanki: I'm one of the old-time 1970-1980s pen and paper D&D players, and Githyanki are a Lawful Evil race.
She fits that for sure, but it's odd that she responds positively so often to "good" player choices, as long as it's not in the narrow realm of strong vs. weak. This is where the traditional DnD good-evil alignment breaks down, I think. I don't see Spartans as evil, and that's basically what she is.
That said, with the current companions available it is very difficult to create a viable 4-person party.
Well, at least the current game design removes the need for one leg of the classic Holy Trinity, a healer class. There are enough potions and the food mechanic that a healer isn't needed in the party. That allows some flexibility in whether to take Shadowheart or not as an off-tank and healer.
How about next patch you do a bunch of game rework and re-balance the encounters for a 5 person party?
Unlikely, I think. I'm sure it's been said before, but the combat encounters just aren't designed for it. Not just the need to boost the enemy with more numbers or strength to avoid making it too easy with a larger party. It's the design of the areas where major combats take place. There just isn't enough room. The entire game world in Act 1 is designed to fit an adventure party of 4 and enough enemies to make it challenging. Modders can increase the number in the party, but they can't increase the size of the maps to allow the room for a larger party and more enemies.