Changing Job Application Tactics?

In reflecting on my prior experiences with searching for a job, I realize my approach may not be as surefire as I thought; chalk it up to me trying to be self-aware.

My usual process is to target only a few companies, connect with a mix of junior and senior employees in person or by phone and then tailor my resume and cover letter appropriately before applying. Though I secured my past two internships using this approach, lately my success-rate for getting to the 'request for interview' stage has been abysmal. Do understand that this is my first go at applying to front-office roles on both the buy and sell-side, so maybe my expectations for a response are a bit generous. Applying to a greater number of firms seems like an obvious solution, but I'm a bit hesitant to simply blanket-submit my resume in all directions in hopes that something sticks. It's not so much about getting rejected as it is the time spent creating a profile, filling in personal information and customizing my cover letter for each application.

Anyone care to share their perspective and/or successful testimonials?