Breaking vines with shears with Efficiency V is still as slow as using normal unenchanted shears.
The enchantment-effect does not work for vines. It works for webs and wool, but not vines and carpet (didn't intend on adding that side-bug here, but noticed it while testing of wool).
In addition an axe cannot successfully break vines with drop, but efficiency works for them. This behavior cannot be intended, it is super quirky and unintuitive - "wrong tool breaks it faster".
This bug exists as
MC-103430 for proper Minecraft since 1.9.4, I am not aware that one could add multiple affected projects.