I think the issue with DRK, MNK and Delirium, allowing it to have the same effect as Dragon kick and thus allowing all MNK's to bypass dragon kick is likely to put a skew on world first raiding when stacking MNK and DRK suddenly become the most optimal DPS grouping due to being able to permanently crit Bootshine instead of Dragon kick. I know MNK isn't currently the top DPS at the moment but Yoshi did just mention he was looking at:
First we will be making adjustments to the effect duration and effect potency of Greased Lightning.
This could easily push MNK back to the top and then allowing DRK to bypass dragon kick for them is likely to entice a lot of people to start excluding other jobs in favour of MNK/DRK