I have been in a situation like that twice at MSU. Took Orgo 1, class average was a 48% (about a 2.2 out of 4.0 when you average it out on our grade scale, but grades are only in 0.5 increments). I finished with a 78%, which was just 2pts away (in a 550pt class) from a 3.5 and my teacher refused to boost me up to a 3.5. My TA told me that of the 250 students in the class only 28 students got a 3.5 or 4.0 in the class. I had two friends who were 4.0 students in Chem and Bio and got a 2.0 in the class. There is a reason it took 3 semesters of class averages from 46% to 49% for him to finally get fired. But again I still got a 3.0 in that class, but the fact that I was probably near the top 12% in the class I still got a 3.0 (or a B).
Then I have had a Adv Physio and Adv BioChem course where of the 250 student class if you are in the bottom 25% you automatically FAIL and in order to just get a 3.0 you have to be in the top 30% of the entire class. And these classes are full of pre-med students that are going to graduate with High Honors (above a 3.65 cumulative GPA) in a year. So i am in the same boat. My GPA was great but now that I am taking the 4 hardest undergrad NatSci courses offered at my school and each one the grades are based SOLELY on the class rank. I have kids in my class that entered last semester with a 3.75 cumulative GPA through 6 semesters at MSU and received a 2.5 grade in the class.
Up until last fall semester I had never thought that I would receive a 2.0 (C) in a class since I have had three classes that were just hard as hell and just barely missed a 3.0, so I received a 2.5. BUT my school doesn't care and makes sure that the hardest NatSci major students have to take the ONLY 4 undergrad classes that you are graded on a class rank.
If I were you I would just ride it out. If you take the W then you have to take this class over again. If you KNOW you will get a C then just go for it. I got one C and a D (2.0 and a 1.0 (b/c my BioChem teacher gave me a zero on an exam b/c the girl next to me was cheating off of me, so I also got the zero BS I KNOW!) last semester while two classes of a 3.5 grade and my GPA decreased by just 0.09...but again I went from 91 to 106 credits
So I am taking a guess that you are a Freshmen since one C would drop you that much. But the last part of your sentence is a smart but also bad presence of mind. Don't go into next semester thinking "Well, he is a good teacher so I'll get a 4.0" I remember I thought my Chem 1 and 2 were going to be simple since it was the teachers first year. Just the opposite, our exams were based on what the other 2 teachers taught their class and about 10% of the exam was what she actually taught us and the other 90% was either stuff we hadn't gone over or the other teachers stuff. Then the next year all of her exams were the easiest exams ever. My freshmen yr our class avg was about a 68% on exams. Her second year, the average was about 84%.