Obviously the rarity matters with regards to the drop rate, but the rarity label itself doesn’t mean anything to me. My issue is with the relative time it takes to earn the various combinations of “best” effects. We’re definitely in a grey zone here – DB is currently not quite in stereotypical pay to win territory, but it is too close for comfort.
It’s difficult to say what exactly is acceptable or not, but I would suggest something like, as a general guideline: An average competitive player should never be faced with a choice of either spending money to buy ingame resources (be it loadout cards or mercs) or playing the game at a disadvantage.
What this means is that every combination of augments and loadouts should be available to a player who earns the average amount of drops, with a minimum of hassle (i.e. absolutely no grinding or having to spend 5 minutes crafting before each game, or similar), within a reasonable amount of time (for example 100 hours played). If this is achieved through a combination of random drops, crafting and rarity distinctions, then that’s fine.