Yes, the upper case input is now redundant. I have a fix for you, but only with new instances as the change cannot be retroactive in to active instances.
Try this (changes in bold).
Instr(1, GV_ReqUser, GV_L2auser) =0 AND Instr(LCASE(GV_L2auser), "not required") = 0
The LCASE(GV_L2auser) forces whatever is in the string to be tested as lower case. So the input can be any case or mix of casing.
By the way, I also removed the 1, from the Instr as it will default to the first position anyway - your choice to leave it in or not.
Also, you may want to LCASE your first test as well:
Instr(1, LCASE(GV_ReqUser), LCASE(GV_L2auser)) =0
Senior Director Support Americas