I would like to share some tips with prospective students talking from my experience as I am in the education field. I get to interact with technical and HR people at job fairs/project exhibition when companies come to hire.
Firstly, both your degree and your institution matters a lot particularly for your first job. When we hire, we sometimes get upwards of 100-150 CVs against one opening, particularly from BS/MS holders. It is not possible to call everyone for interview so we do shortlist. Fortunately or unfortunately, it is on the reputation of the institute and then GPA. Most of the time, the unspoken rules are: only shortlist graduates of FAST, LUMS, GIKI, NUST, UET or if an exceptional GPA then PU/COMSATS/etc. Iqra, Preston, UCP, UoL, USA, etc are a strict no and nobody reads their CV beyond the first page. Sad as it may seem, its the reality.
Secondly, HEC ranking might be important for outsiders. Insiders go on reputation and past experience of previous graduates. HEC ranking does not necessarily reflect quality but rather quantity. Software houses, MNCs hire graduates from these institutes are higher level than from a different institute. Many times, I have had the odd request to "help us with a list of above average students who have done market oriented projects" we should interview. In some cases, I have been asked to sit in the interview session and help with selection (from people who have developed friendships over the years).
Once I asked them about their strategy and the reply was: "interviews is a time consuming and unpredictable task for us. Usually, we send a small team of technical + HR people to project exhibition/open houses of top tier universities, observe the projects, and make a list of shortlisted candidates for interviews whose work match our profile". They do not even bother to go for traditional advertising, etc.
However once in job and after getting experience, the degree becomes less important (though still not irrelevant) and your practical experience and achievements are more important. So in summary, its not like students of less reputable universities do not get a job but the first entry is relatively difficult. There are certainly cases where lower rated (GPA or degree or institution wise) have excelled in life and achieve much better.
My advice: If you have the opportunity and means, go for a better degree and a reputable institute. Undergraduate degree does matter. However, the most that matters is you yourself...your character, your personality, your hard-work, dedication and your achievements. Your degree or institution can only help land your CV for interview...rest is up to you.
All the best.