I don't think I would particularly recommend that strategy.
First, your GPA. I agree that it is possible to be accepted with less than a 3.0. (Usually that means 2.9something and not 2.5something) It is also possible to find a winning lottery ticket on the sidewalk. Just as I wouldn't recommend the lottery ticket strategy as sound financial planning, I wouldn't recommend counting on an admissions committee looking the other way when they see a 2.5.
You need a higher GPA. If that means graduating later, that's what it means. You can chose to graduate on time instead, but one of the consequences of that decision will be a substantial reduction of your chances of getting into grad school.
Second, you need to really smoke the GRE, especially with a low GPA. The average grad student got somewhere in the 70's (percentile). Getting in the 75th or 80th percentile isn't going to impress an admissions committee: they can just as easily accept someone with a slightly lower GRE and a much, much better GPA. (Remember, admissions is a zero-sum game: there are N slots that the committee fills, and if you get a slot, it means someone else doesn't). We're talking 90's. Maybe high 90's. And maybe high 90's aren't enough.
When you took that material, the professor obviously felt you didn't understand it well, or your GPA would be higher. Making sure you have a solid foundation is key to success in graduate school, and it is key to scoring well on the GRE. Spending a year retaking classes in which you did poorly is a far better strategy than trying graduate-level work with a shaky foundation. It also compensates for a poor GPA: "I didn't know it then, but I know it now".
Good luck!