Assaf:
Your final comment about trying to cover as much vert as you can in the time allotted is actually the goal. The feedback on the legs being the limitation is simply what nearly everyone I have ever had feedback from feels when doing this workout. Good Luck.
Scott
Just:
You say that you had to move unreasonably slow to keep the pace sustainable. Why? What was limiting your pace?
You can’t compare outdoor climbing speed to a stairmachine. Outdoors you will be hard pressed to find a slope over 50%. A stair master is close to 100% grade. Much, much steeper than outside making it harder. Plus the stairs are falling away from you as you step up on to the next one. You actually only raise your body about 1/2 of the step height. Otherwise, you would hike right up and off the end of the machine In short you just can’t compare these two.
Scott