Shortbows are shit. Barely half the damage, no evade capability, less AoE area. Death Blossom is an evasion move, shit doesn't hit you while using it.
What!? Have you tried it for some matter of time? Its easily one of the most integral weapons in the thief's arsenal. Blast finisher, projectile finisher AOE auto attack, poison field, extra dodge
that adds cripple, and a target-able shadowstep. Sure the damage isn't as high as your melee weapons, but if you grab haste watch as groups of enemies melt before your eyes as they feebly try to catch you. Without it in PvP against any competent opponent I'd last 10 seconds, even less in group engagements in tournaments.