In my experience you only really see imbalance when you increase the points by a small amount. Like going to 105 points which lets you add in another academy pilot with howlrunner, for 8 Ties, and Howl with SD. But you can't really add a ton more to a rebel ship with 5 points.
But if you stay with multiples of 50, such as 100, 150, 200, 250, ect... It seems to work out.
My 5th rookie would disagree with you