They milked the fuck out of those blister packs in ME3's multiplayer too, don't think they didn't. Remember the constant "bonus weekends" they did to push people into grinding for rare spectre packs and whatnot? They incentivized spending more into the blister packs by making it so upgrading rare weapons was only really possible by getting more of the same cards via rare packs.
It was a positive feedback loop since Gold+ difficulty missions later depended on rare characters with rare upgraded weapons to farm efficiently--and since the missions were PvE noone really complained that the entire process was essentially pay-to-win.