Well, I'm not a great fan of the theological drift hypothesis. The 11th century was, as proved by history, a dynamic time of extreme change from a very militant party of non-Roman, Latin reformers who took over the Western Church in the mid-11th century and transformed it into that which it had never been before by 1100. Sure, there were some precursors to this, most obviously along the lines of papal supremacy. However, in general, I think the practices of the Western Church prior to that critical time are without question Orthodox, since they were fully Orthodox. If one goes to far, one sets up a sort of double standard. Why would the East be immune to such heavy scrutiny just because it has remained Orthodox? For the first 1000, it was a hotbed of heresy.