New Mord ult is buggy

i was playing vs. . ults me, starting the 1v1. when i cast my ultimate, my clone appears but wont attack. when ult ends, the clone vanishes, but doesnt die. the cooldown doesnt start until the full duration of my ult elapses, and no boxes appeared. i understand its supposed to be a 1v1 but im still only one player, why does the clone not work? why should his ult make mine useless??