According to wikia:
The second word allows the will of people and animals to be controlled. It makes them temporary allies to the Dragonborn
I have the three words in the shout. Not tried it on dragons yet, but I have tried it on some enemies like Draugr and end bosses in ruins etc. It doesn't work.
Can it actually be done or am I wasting time trying it?
Best Answer
According to UESP, the 1st word will let you cleanse All-Maker Stones, the 2nd word will let you force NPCs and creatures to become your allies for 30 seconds, and the 3rd word will allow you to force dragons to be your allies and to ride them.
Draugrs aren't NPCs or creatures, they are animated inanimate objects lacking any will, so it's not surprising they cannot be controlled by the Bend Will shout. Additionally, it only seems to work on NPCs that are hostile and unnamed (guard, bandit).