Level 31v heroic, mob of 4, poison dot, with 31^^^ wandering rock crawler in area. This is the second mob in this tunnel. Mob scales with level, so level may change to match yours, I chose the non difficult crawler nest version, and my level is 31.
These spawn heroic mobs one level below you when you get near them. You can , if you're careful, set off one at a time. Don't run thru them right into another mob though.
central mob of linked heroic spiders in this room, scales with level, two levels higher than yours, web in this room is inaccessible, at least when you walk in, the room is full of egg sacs which become hatchlings and attack when you get near, a steady stream of defenders will continually attack one at a time after you kill central mob