The videos below showcase the optimal path to take in each of the different caves during the Death Mountain Climb, to catch the boulder cycles. The current fastest route involves a skip that combines both cave 2 & 3, but the old route for those two caves are still listed below, as well as the new one.
You can also merge the north wall to get across the 3rd gap, but it is roughly a half second slower than Dash Sliding over it.
This is the old route, without the skip.
This is the old route, without the skip. The boulders cycle will be different for the skip route.
Not getting the skip on your first try will mess up the boulders cycle in the later half of the cave. Getting it on your second try still saves a bit of time, and third try more or less breaks even.