[snip]
A couple of concerns regarding the methodology. First: using only 2 of the 3 "big" compilers. Second: using versions of the compilers that are 2 and 4 major versions behind. And third: not comparing against "import std;".
As for floating a proposal on this list, having things like <algorithm-core> that includes only the contents of <algorithm> as defined by C++11 would be a way to cut back. I can't say there are any clean and satisfying solutions that come to mind right now.
That's a discussion for the compiler vendors, not the language specification. I doubt we're going to go back and specify the existence of <algorithm-cpp11>. Offhand I don't see an issue if a compiler vendor chose to implement their version of <algorithm> as a sequence of "#if __cplusplus < 2011xxxx". (whatever the constant is) "#include <algorithm-cpp11>" "#endif" "#if __cplusplus < 2014xxxx" "#include <algorithm-cpp14>". From the Standard's perspective: user #includes <algorithm> gets the appropriate algorithm bits.