The Dark Below:
Necrochasm - nothing but a joke (right now)
Dragon's Breath - the "I'm gonna pretend it's as good as a Gjallarhorn because I don't freaking have one" rocket launcher
No Land Beyond - Troll gun
Fourth Horseman - pre-buff: below average PvE shotgun / after buff: amazing but no Found Verdict
House of Wolves:
Lord of Wolves - decent but would get easily replaced with Ice Breaker or Gjallarhorn for Solar burn Nightfalls. Only useful for when fucking around in PvE and okay in PvP
Dreg's Promise - use a Vestian for the grimoire instead
Queensbreakers' Bow - best of the new bunch. A beast in arc burn Nightfalls.
Other:
Fate of All Fools - does not exist for 99% of the players in the game
Gjallarhorn - NEARLY 1 YEAR IN AND STILL KING, BABY!
if they want folks to change loadouts in PvE, they need to a) not make any more bullet sponges and b) make exotics as good as Gjallarhorn. I honestly don't see a nerf affecting Gjallarhorn's PvE status that much if the new exotic weapons turn out to be on the same level as the previous expansions' exotics.
The best exotic weapons in the game still remain Vanilla Destiny exotics. If they want us to change loadouts, give us better weapons. Yeah, HoW has better weapons for PvP but for PvE you still have people rolling with Fatebringer, Found Verdict, Gjallarhorn, and all the PvE mainstays. I need a good reason as to why I should replace Gjallarhorn with something else for PvE. Nightfalls don't count. If the new weapons are great then yeah I'll use Gjallarhorn less and less. But if they turn out to be like all the rest from The Dark Below and House of Wolves, expect people to still be using Gjallarhorn for almost everything PvE.
In my honest opinion, the nerf won't do shit to all those LFG posts. People will still be asking for Gjallarhorn wielders only.