One strategy that I've heard about but never tested is this: You find an actual ticketmaster outlet. My older sister told me about doing this in the 80s, when there was a ticketmaster outlet in every other strip mall in America. Now they are few and far between, and the only one I've ever seen is at the Beverly Center Mall in Los Angeles. Anyway, the outlet's computers will be logged in to the same system that puts the tickets on sale by phone and web at whatever hour they go on sale. You just call or go to that outlet at the right time, and there's bound to be less traffic there than online or through the 800 number.
Worth a try.
This is my first post here, by the way. I used to post on the Coldplay.com board, but that, like most of their fan outreach, seems to be a thing of the past. Here's to scrounging for GA-PIT tickets with a whole new community.