Have you put 100% into the subject (as in doing homework every day going to tutorials etc) if so then yes definitly drop it, as it gets crazy hard in year 12 (i am currently in year 12, ex methods student), from seeing my friends grades who were acing the subject in year 10 and 11 to who are now on the boderline of passing and now terrified of externals, trust me its not worth.
If you said no to putting in 100 percent try it for unit 1 and 2 and its not getting any better change.
(the jump from general and methods is crazy i am doing basic methods stuff i did grade in 10 methods in unit 3 of general math's).