Shouldn't an Vimpire with deadly make it grow when it destroys a plant?

Yes.

It doesnt.

It needs to have power equal or more then the plants toughness as if didnt have deadly for the ability to work.

Is this a bug.

I'm going to go try it out now. It's definitely a bug if it doesn't work.

There has been quite a few bugs associated with Vimpire in the past. So it wouldn't surprise me.

OK, I finally got to try this out (people were not being very accommodating).

I experienced the same thing you did. Vampire did not grow after destroying a cactus (he did attack again though).

This is definitely a bug.

@EA_Andy Can you please let us know if you've seen this and passed it on to the developers?