Mobs gladly walk across Big Dripleaf paths, regardless of if they will fall a significant distance. However, they do not attempt to jump up 1 block to walk along dripleaves. 

What I expected to happen was...:
If mobs are supposed to treat dripleaves as solid blocks, I expect that they would be able to path and jump up to the dripleaf block.

What actually happened was...:
A mob completely surrounded by 1-block high dripleaves stays there indefinitely, until one of the dripleaves around it gets activated and then the mob gladly walks out of the enclosure.

Steps to Reproduce:
1. Easy to setup what I described above, surround a mob with dripleaves that are able to be jumped onto (1 block higher).
2. I also experiemented with 2 stone pillars (>4 blocks up), and a dripleaf bridge connecting them. Mobs gladly walked across/fell through the dripleaves when the bridge was the same height as the pillars. They refused to move when the dripleaves were 1 block higher.

So just a summarizing note, I'm not sure what behavior you intend mobs to have with dripleaves, but I would recommend having them included in the valid pathing space only if they will not encounter fall damage. Also, this is a pretty uncommon occurrence in normal gameplay, but I could see some players utilizing this behavior somehow for various mob farms.