One can easily (assuming you have feather fall) jump from the top of that pillar ove to the Lone Tree site. What I was also considering was leaping down and across from a lower ledge, but the gap/angle of descent seemed to wide and or shallow. Actually the jump was only the reason I was bringing it up. Getting to that high spot was essentially impossible via sneaking. If you clear out the defenders, usually about 4 melee and 4-6 caster types (mixed clerics and arcanes) the high spot is clear, but going up solo against that many casters using Holds, Scorching Rays, etc, is vedy vedy hard. With some diligence you can pull some and spread them out. Duck into the cave for a few moments to regroup and sneak back out. Pick off the stragler and rinse and repeat until you clear them. Doable, just not very sneaky.