I like to see how many dungeons i have done in total.
 

In statistics you can see how many dungeons in total you have entered, but you can't see how many dungeons you have completed. Except for expansion widely, like Cataclysm dungeons completed, Mists of Pandaria dungeons completed etc. Would it be possible to add function to see how many dungeons you have done in total?

Is there a problem adding the values together? Doesn't seem like a hugely necessary addition.

I can see every expansion, except Classic and Burning Crusade.

That's because Blizzard didn't track that data, and thus there is no way to backtrack for vanilla and TBC.