The leveling is handled very poorly in this game. There are way too -blam!-ing many soft caps, and the RNG isn't structured at all so a lot of people get very streaky luck. One day I turned in 19 prime/powerful engrams, I was 525 which means all or at least most of them should have helped me. Only 4 of them did, because I kept getting shit that I didnt need. 10 of the 19 were secondaries, my highest level gear piece at the time by far. On the flip side some people get everything they need in one go no problem. A good RNG system mitigates those kinds of streaks to keep the experiance more uniform across all players.