as i said above never trust any consultants in this matter. most of them makes thing by themselves . I don't know from where these consultants got mail .
Yes backlogs do affect visa chances may it be 4 or 14 or 24. But a STRONG SOP is all that will save you. There are many persons i know who have got there visa despite having large number of backlogs.
What matters most is if person has completed his/her studies in regular time like b.tech in 4 years