For anyone who struggles to find these guys, this was where I found it worked best for me.
The Boss Bears are level 15 and hate fire, so a mage might be handy to speed it up, they have ~71,000hp and can be slow to go down.
Emerald Graves seems to be the best spot for me. Double check and make sure the trial for Grizzly End is on, I found occasionally they turned off for me, then when you know it's on, travel to Briathos' Steps camp, and go west around the edge of the mercenary camp, then follow the hills around to your left to Harrow- there should be a steep hill going towards the south just before the edge of the map. I found 9/10x there's a great bear waiting for you. They're hard to miss- in the tactical camera they're called Boss Bears, not Elite Bears, FYI. If you get lost, check out the map with rifts on it-
http://dragonage.wikia.com/wiki/Emerald_Graves[On the left side of the map, about halfway down there's an exit from the map, the rift just to the right of it is where I'm talking about.]
Then pretty much comb the hills straight north towards Gracevine camp, continue past that to the big river, there's usually one or two around here, and across the river to the north where another rift was there's sometimes a bear, sometimes a giant.
When you've done a run from south to north, I found you have to leave the area and come back to repopulate the bears, so quickest I found without reloading the map, is to pick the farthest camp away from them on the map, which is the southern one you start at, give it a few seconds until you know it's loaded up the sounds and textures, then quick travel back to Briathos.
Shouldn't take more than half an hour to an hour if you get lucky spawns.