It's not that using too many is the problem, it's a problem for those who get mostly armour engrams. If you're not getting junk weapons to dismantle than you're not getting Parts. It's possible to run 4-5 strikes and only walk away with 2 weapon engrams, which now end up being 2 or 3 Parts. If this isn't a problem you've dealt with than RNG is treating you better than some.