If there is a GOOD REASON for Devastator I think they can definately make it work. In the comic book, they were brilliantly introduced. Build communications bridge... when attacked turn around and defend it in the most dramatic way possible.
If it's done purely for effect and "gee whiz" audience reaction (which is typical Bay) then I say No. I'd much rather see Shockwave trounce everybody.
Agreed. I will also add that there becomes a point when there is just too much... and since we're talking Michael Bay I will admit he's already over the top, so adding Devastator would, in my opinion, be way "too much."