Hi Orochimaru,
Well first off, I think you're being too hard on yourself...I think you've got a lot of strengths like your dedication to extracurriculars, an excellent GMAT, plus a clear career goal. Remember that nearly every applicant has some weaknesses or areas of concern in their profile...nobody is perfect!
My understanding is that backlogs will appear on your transcript much like failing grades or incompletes do in the US...are you able to replace them / retake courses? If not, then I think it depends on the reason for the backlog and how much it affects your overall GPA (your's still seems pretty good overall). You can always write a brief optional essay explaining what happened. Also remember that undergrad performance is just one factor in the admissions process so if you have an otherwise stellar application then I think you can definitely land somewhere good. Top 10 may be out of reach but there are plenty of amazing programs outside the top 10.
One other thing...if you'll be working in IT but plan to switch into marketing post-MBA, try to think about how you can take steps towards that goal, or at least get exposure to some of the skills that are going to be necessary in marketing. This may not fit with your position but perhaps you could do things outside work like join a professional networking group related to marketing or volunteer for a non-profit that needs marketing help...these are just some ideas to get you started on how you can make that transition easier (and more believable too, from the school's perspective).
Good luck!