The adds seems to be coming faster and take longer to kill now (since the reset). We do the HOs, but hoping for the Core Synergy one to able to keep up with adds seems not right to me. We do kill the portals etc. The other problem with the fight - is the fear from the adds. As Immunity Runes are now no-trade and honestly rarely drop, can the freq of the fears be reduced on the adds. Note - entire group was at resolve and have done this zone successfully previously.
Not slowing down the adds, but for the next update, Trail of Death (fear cast by adds and some base population) will be changed so it won't stack from different casters and won't be reapplied if you're already afflicted. That change will be in all instances of the zone.
I guess above I should have been a bit more specific - slow down the "frequency of portal spawns" (and their HP).
The source portals and fragments of the source that spawn during the encounter with Terranus can now be severely damaged with both Core Synergy and Core Power IV, in all Heroic versions.