Does he spawn on the tops of the rocks or out in the open area? I've done many loops in single and multi player and have yet to see him. I vaguely remember seeing him chase other players maybe a year ago, but I suspect that they had already pulled him from somewhere.
iirc it is somewhere on the top of a rock, not roaming around. some time past when i was there the last time so i may confuse it with the Dragon in Wyrmsands who is on top of the Rocks and you have to climb up the rocks at the ruins. But in my mind the Phoenix is also somewhere hidden, where you need to find, where to climb up, but i may be wrong, it is many month ago.
In the middle of one of the rock mountains, there is a little alcove with an oracle statue head at the end of it, when you go in there hang a left and you will see some steps, on the steps you see 2 little rock pillars, jump on those then another rock pillar lead onto a slope of broken wall, get up there, then you can jump from there onto the top of the mountain, and the Phoenix is up there.