I wanted to try and check if my party can finish duncan's part of the dungeon.
Completely forgot frozen soil but it turned out not needed. I managed to get to duncan without any deaths only to realize that my W/D enduring scythe doesn't have swap
My party was:
1) me as enduring scythe W/D
2) Ineptitude Mesmer (the same as yours)
3) Panic Mesmer (I imagine PI will work just as well)
4) SoS Rit with smiting (SoS, Bloodsong, Ancestor's Rage, Splinter Weapon, Spirit Siphon, Smite Hex, Smite Condition, Strength of Honor)
5) UA Monk healer
6) ER ele prot
7) Curses necro with Spiteful Spirit (I know it doesn't synergize well with Panic but it was just a try and dwarf mobs have no way of removing it anyway)
8) AoTL Minion master with dwayna's sorrow
I rolled through all mobs without any problems. Then Duncan rolled through me

. Next Time I'll roll W/A with dragon slash and swap. I did not use ANY consumables.
My suggestion would be to drop Discord altogether. Stone Summit mobs cannot remove hexes but they remove conditions very fast making discord less useful. Also dropping discord will allow you to use some actually useful elites. SoGM rit looks a little weak too.
Pull mobs yourself and ball them so that your HB and Splinter hit them all. With 2 shutdown mesmers mobs won't do much