I've seen a massive dropoff of fusion rifle usage, and assume the majority of those players picked up shotguns which have become ubiquitous in the crucible at this point. The presence of quick kill mid range primaries make these a waste of a weapon slot. It takes about as much time to charge and fire a shot with a fusion rifle as it does to fire a few bursts from my red death, or a thorn, out pump out half of the last words magazine. All of those options are more consistent at getting kills at mid range as well, and when fusion rifle engagements can take 2 to 3 charges to down an enemy, you can be sure people have stated shelving them for the raw power of shotguns.