In ANH the Proton Torpedoes were able to perform a turn calculated at 72000 gs to enter the Death Star exhaust port - I would say they could definitely chase down fighters.
That's the kind of thing I'm talking about, just because it happens in a scene in a movie in which it
needed to happen doesn't mean that people should jump to a load of conclusions based on it. That way leads to turbo-lasers capable of vaporizing large percentages of a planets hemisphere with a single shot, and armour so powerful that it would shrug off hits from those Turbolasers. Personally, I think this is done purely to win arguments in 'whose favourite imaginary sci-fi race is best?' type situations.
Proton Torpedos should be, in my opinion, what they
need to be, big, slow, anti-cap missiles, you don't shoot torpedos at fast targets, concussion missiles, maybe, but even the name 'torpedo' suggests anticap weaponry.
Basically, even if it goes against what many of the 'mega-whopper-turbolaser' clan like to believe, I think torps should be slow, and heavy, and concussion missiles should be fast, but not last as long as they did in XvT etc.