Underated by whom?....i mean guys who know what great bass playing is...all know how good this guy was. His playing helped put Elton John where he is today.
I dont think he's underated at all...simply put, he's one of the greatest rock bassists of all time....PERIOD
And...in my opinion...Dee's recorded bass tone was consistently the best. I've never heard a recording on which his bass didnt sound fantastic...even when he discovered the steinberger and was slapping it all over "Too Low For Zero"...he sounded great.
His playing on "Grey Seal" just kills me. He was the perfect bass player for Elton John. With All due respect to Billy Joel and Doug Stegmeyer (who immediately spring to mind as the obvious contemporaries of EJ and DM)...I dont think they were in the same league. IMO
I think he's somewhat underrated by non-bass playing musicians. It seems many guitarists, drummers, etc. don't fully appreciate just how great he really was. Bass players though? Anyone who takes the bass seriously would recognize him as one of the greatest of all time. The interplay between bass, piano, and drums is beyond description. His playing is an inspiration for all music lovers.
BTW I think his tone on Funeral for a Friend/Love Lies Bleeding is about the best I've ever heard.