On hard mode, Fatebringer is a no no during the Oracle phase for both the Templar and Portal Teams. That and one blast from a shotgun at point blank kills off Oracles faster than any other weapon with or without Oracle Disruptor. Shotguns are also good if your in the portals, just jump and one shot an Oracle.
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Shotguns used to take multiple shots to kill and Oracle before they buffed them in PvE. During the Atheon fight, the oracles are to high up to shotgun efficiently (if you don't one shot, you are wasting time by jumping). And you can still use Fatebringer for Oracles. Sure Vision of Confluence and Praetorian Foil work much better, but it's still doable. It's particularly useful fighting the adds that spawn during the Conflux waves and Oracle fight (assuming you don't go back to the top to snipe). Plus it kills supplicants faster.