OK.. because i was such a masochist i did lvl 60-70 prot specced. umm.. in order to prove a point.

And there really is no point. I had quite a lot of lvl 60 tanking epics so shield slam damage was "ok".

For 60 to about 65, with my lvl 60 dps epics it was quite easy to just do dual wield prot grindage. After that though, I noticed that while i could Dual wield and devastate spam, i noticed that i wasn't killing fast enough and taking far too much damage even in dps gear. It would definitely have been a lot faster soloing in fury as you definitely kill faster and therefore take less damage and have less downtime. So in the end it was faster to just do sword and board dps as prot.

(having said that, now that you also have sunder effects with devastate, it is would definitely make a big difference to damage output - previously you didn't)

The other thing about prot solo levelling in sword and board is that it is possible to solo most the 2 and 3 men quest elites, which i found incredibly useful as i got my copy after most of my guildies had reached 70.