Hi G Mulee,
I am in agreement with you concerning "welder qualification per D1.1". Table 4.11 does not list base material change as an essential variable requiring requalification for the welder. All the base materials listed in Table 3.1 are prequalified materials.
But PQR essential variables requiring "WPS requalification", Table 4.5 (30) States: "A change in base metal or combination of base metals not listed on the PQR or qualified by Table 4.7".- therefore a change in materials would require requalification of the WPS. And for PQR's where CVN's are required additional essential variables in Table 4.6(1) State: "A change in Group Number". Also see Table 4.8 for more guidance on PQR base materials.
To answer your original question, I feel like the welder's range of qualification would be to weld any of the base materials and combinations of those listed in Table 3.1 if he/she was tested with (one/or combo) from Table 3.1.
If I have over looked something and am off base, I hope someone will post and help guide us to the correct info.
John Wright