I'm on the bandwagon for the series preference, 1 was decent, 2 sucked moosecock (I can use male and female derogatory terms whee), and 3 was one of my favorite titles for ps2. Shion was in fact a useless broad who should have really stuck with being seen, not heard. chaos was a favorite in 2 and 3, cuz his voice actor in 1 ruined the depth of who he was, which pissed me off. KOS-MOS will always be my favorite FEMALE robotic lifeform, with male robotic lifeform stuck on Robo of chrono trigger. Everyone else really gets shafted sadly, I mean, fucking Jin doesn't even get screen time til 2, wtf?! That being said, he was a champ at the end of 3.
Overall, xenosaga 3 is worth playing, but 1 and 2 are missable. Oh, and dice, since you're the first person to actually ask that a term be refrained from use, I will forever switch the c word with a word of the week. This week....mallowmar.
Example, "Shion was such a useless MALLOWMAR."