One thing I really liked about the RNG and microtransaction store was it kept all the DLC free. That kept the comunity in a single bubble of DLC, whereas other DLC splits the gaming community apart between those who pay for it and those who dont. DLC is oftne the killer of playlists in games like Halo/COD, whereas Mass Effect kept its active commnity together.
Additionally, keeping it random forces players to play and try new things as it comes, rather then just buying a specific kit/weapon, palying for a while then quitting. The element of randomness forces a progression arch.
If I could change only one thing about the microtransation RNG store, I would like to have paying customers get a random UR no matter what, rather then just the standard RNG pack. After all, they are the ones funding the DLC, so they should have some reward. And as someone who only payed for a whopping two packs, actually getting something out of those packs might have got me comming back for more.