I went back earlier this evening to try again, and this time I figured I'd try a different mob. So, I headed over to Granitesmash's spawnpoint and killed his PH. Fight was somewhat challenging, although I didn't have to burn any AAs/discs besides protective spirit. I then sat down to wait for the named/PH to spawn again, but I decided to suspend my pet to save buff timers, and to remain visible just so nobody would get any ideas about taking my camp. In retrospect, these were both very dumb things to do

. A dragorn snuck up on me, and although I was able to get my pet out and get him slowed, the whole thing went south when he ran at low health and aggroed another mob. I managed to gate out, and I decided to return and try again.
This time, the Kyv Bowhound was up, with nobody camping him. So, I figured I'd give it a shot, and in fact I was able to solo him, although it was very close. Unfortunately, I ran into the same problem I had with the roaming dragorn: when he ran, he aggroed another mob just before I could kill him. I managed to loot him (only dropped a spire control shard) and gate again.
Went back a third time, this time with a 66 necro friend. We initially were camping the Bowhound, Granitesmash, and Onaria, although we lost the Onaria camp to another group later. In our time there, Granitesmash never spawned, but the Bowhound did spawn a second time, and we killed him (this time he dropped a caster range item). Strangely, the second fight with my necro friend helping was actually more difficult than when I soloed him.
Anyway, thanks to the poster who mentioned this spot, it looks like a few friends and I may have a new hunting ground.