I recently watched X3 again, and my memory of the film seems to be more favorable for the film than the recent viewing (which is shocking, since my initial response was that it sucked)
I originally thought Angel went to the X Mansion to inform the mutants of some sort of plan by his father to force the mutants to accent the cure and form some sort of contingency plan, but as it turns out, he was just there to ask if this is a school where mutants go. Apparently his limited role was even more limited than I thought. He had less than 5 minutes of screen time and one of them was in the teaser before the opening credits. Last time I checked, using characters in a teaser before the credits was an indication that said character would have lots of screen time and be fleshed out, it's like basic story-telling 101.
Also, the wire work for this film is atrocious and the most painfully obvious I've seen since Superman 4. While S4 was bad due to the fact that the wires were visible half the time, here it was bad due to the fact that the actual use of the wires to make the characters jump was done so poorly that it looked blatantly fake.