Its been pretty much the same in ME3 multiplayer back then. It was a wise choice to go for the smaller packs (cannot recall their name) to unlock and max out all the common+uncommon items,characters first. Then start to buy the more expensive ones so you actually have greater chance to have rares and ultra rares and not wasting 99k credits on uncommon stuff.
I'm more worried about the ultra rare packs. I've had several that only had gold and blue items. It's saddening if it becomes a supply pack as well even if there are still ultra rare items left to unlock.
