Lit is a lot harder than English.
And it was nothing like year 11 lit for me.
noooo why do you say its harder?
I found the opposite was the case for me.
Lit allowed a lot more freedom with texts (ie you don't even have to read a text you're not interested in). I also felt that exam structure was easier to deal with... but time will tell (hurry up dec 14th!)
Also you don't have to do an oral!
I wouldn't advise both if writing doesn't come 'naturally to you'. And judging by it being your worst subject I doubt you will. I spent about 80% of my study time on eng and lit throughout the year (mind you about 90% of that was procrastinating).
Keep in mind that literature allows more freedom with essay structure and for some (like myself) who've been writing the same way for the last so many years (the 'english' way) it can be a bit difficult to adjust to the more free-form type writing.