As ugly as it may seem, this is actually it. Yuck. You shoulda seen the map before I tried to make it a little clearer to understand. Nightmarish box. I will be ID'ing the mobs here soon, but for now, here is at least the map of the area.
If you use my maps, you should be fairly familiar with this by now. Start from just inside the West gate of DH, and head ALL the way west until you cannot head west anymore to #2.
All the way west out the gate will lead you to this mother of all trees. (Though I would personally contend that the Tree of Life is the REAL mother of all trees, but more on that later). There are actually two ways up into the tree. One is to head around to #3, and the other is to head over to #4. This is the way up up into the tree. Up all the way from here will put you beneath the canopy. West from here is a pain in the butt little doorless room. If you do go west, you can recall out. But its usually easier just not to go west from here :) If you come this way, you will have to open the tree and enter. Up from #4 will also lead you up to beneath the canopy. Yeah, this is the way to go if you are looking to head up into the upper canopy. If you are having a hard time killing things down in the lower canopy, then don't even bother heading up from here :).