I plan to XP in this manner:
1. Review
this thread and
this section and pick a spot (if you don't already have one in mind).
2. Have a plan B to exp in since things can change quickly in your plan A spot.
3. Form your PT.
4. Do a /sea ##-## <area you want> - count people and PT leaders and check their comments as some PT leaders (including myself) put our camp spots in our search comments for the more intuitive players on the server. Or you could just send a /tell to the PT leaders to see where they are and how much longer they think they'll be.
5. If it's crowded, go to plan B (see #2).
6. If all else fails, review #1 again to find another spot.
Also, it opens your options up if you do a /sea all ##-## for your level range at random times throughout your time online, and you get to see who's XPing in different areas. There's areas out there where alot of people haven't even heard of that give great XP.
As for dealing with the situation you've presented in your OP. The best you can do is move as far away from the closest PT as possible and eek out what XP you can. If you're out of sight of the other PT, they usually pay less attention to you, regardless of whether you're outpulling them or not.