How short of a rod would you use for deep diving crankbaits? I have a 7'10" but feel as if it's too big. 

I have a 7' for shallow running ones and plan on buying at least a 7'6" rod for deep cranks this year.  Personally I don't think the 7'10" rod is too big. 

7'2" rod for me. I bought it originally because it's the longest rod that will fit in my boats rod locker. Having said that I really like that length and probably would not go any bigger. Just personal preference.

I use a 8' for deep 20+. Everything below that gets 7'-7'2

I have a 7ft for shallow and medium. Deep stuff gets a 7'6

I'm looking at a 7'6". Is Medium good enough or does it help to have the extra power of a medium heavy?

I use an 8' rod for deep divers.

For the deeper stuff you are gonna want a mh with a moderate action. Usually these baits are bigger and definitely pull harder and a mh will help with those.

I use a 7'6" glass rod for the deep stuff.

7'7 m/m for stuff up to around 12ft

7'10 mh/m for anything deeper

I have a 7ft for shallow and medium. Deep stuff gets a 7'6

Same. I had a 7'10" for deep, but storage in my rod locker was an issue, so I went back to 7'6", which is what I had before, and it fits much better. I can cast just as far with the 7'6" as the 7'10" so that's not an issue.