My opnion is that Theory is important though it doesn't means that a drummer would be able to play better with Theory......because a drummer is also a Musician in a way.
All too often, drummers are seen by othet musicians as just...Drummers and not really knowing what Music is all about. I believe it is important for us drummers to understand not only Theory on Drums but also Music Theory (no need to be an expert on this - but try to understand something on this area).
I only realise this when I join Bands and started jamming with them. Depending on the type of band - one of my bands - the band members communicate using certain Music Terminology (that I could not understand) and I found myself looking a little stupid not understanding what they are talking about.....but I learn along the way and my band leader was very kind to me, being very patient guilding me all along the way.
So I now have a Teacher who not only teaches me drumming as in solely drumming but Music.....I know I have a long way to go - but I am really enjoying it....
I hope by learning these Theory, I can communicate better with my fellow band members understand them better so that I can work better with them all..........most importantly I hope they will view me as a Musician and not simply just a Drummer.
Cheers !