Winged uberpletionist best-in-slot everythingist bow build takes ~3 shots to kill a hard difficulty mob, ~6 for elite, ~9 for low reaper in IPS mode by end of heroics. Reapers take about 15 shots. Group of 6 mobs 2 reapers hitting 2 mobs at a time with IPS is 4 sets of kills, for 15 shots for reaper 1 + mob, 15 shots for reaper 2 + mob2, 9 shots for mob3 + mob4, 9 shots for mob5 + mob6 = 48 shots. 1 shot/second in heroics = 48 second group kills while leveling with a bow.
3 seconds with spells. AoE helpless CC + AoE1 + AoE2.
By the end of heroics, it is ~16x more fun killing a group of mobs in heroic low reaper on a bow than a caster. Way too much fun!