Necrochasm will have the same problems pulse rifles have. Low damage per pellet, moderate dps, low mag size. Basically this will translate into a weapon that is irritating to kill multiple normal enemies with in a row, or a single major (yellow hp bar) enemy without frequent reloads. If the thrall explosion proc will make up for the first of those 2 problems remains to be seen. But I can tell you right now the weapon won't be very good, at least not outside of arc burn modified missions. It needs a mag size bump 20 more rounds minimum.