Don't know if its added, but if you got Elite Hunter (you need to have 50 tasks done) rank in Paw and Fur Society, you should be able to kill bosses using 'boss points'.
ONE TASK = ONE BOSS POINT
ONE BOSS POINT = POSSIBILITY TO KILL ONE BOSS (ANY BOSS, ONLY IF YOU HAVE ELITE HUNTER RANK)
One boss point in Elite Hunter rank gives you possibility to kill any boss from your level range multiple times (cost is 1 boss point = 1 any boss), but only one-time from lower level range (you don't loose you boss points). Doesn't matter which task you choose.
Ex. You got 135 level and you have done Hydras task, after report it to Grizzly Adams you got one boss point and you can spend it on boss from your level range(130+, and lose you point) or/and* kill all bosses from lower levels (< 130), but only one time.
* I'm not 100% sure.