I should say b=c.
When something isn't needed, the simple existence of it is a design flaw.
Is crafting needed during leveling? No, it could be useful, but it's not needed and the work required for this is just too much. Heck... I remember my 14k HP tank Jugg back when I started my first HM FPs, full of blue/green loots and with perhaps some Centurion stuff... but it worked (ok, I died on the -dark- first BT boss mainly because I didn't know it, but we went through it).
Is crafting needed for end-game? No, and it's even becoming totally useless if 2.0 goes live as it was on the PTS.
Conclusion to this? Read the thread title.
Is crafting needed during leveling? No. You can level your characters from 1-50 without ever touching crew skills.
Is it useful during leveling? Absolutely. If you work it right, you can craft gear for a given level and everything that drops is inferior to what you crafted for the next five to seven levels.
Is crafting needed for end-game? Absolutely. I will admit that not everything crafted at end-game levels is worth crafting, but that in no way means that crafting is useless at end-game. I will also admit, that top tier end-game crafting is a very narrow supply market due the limited methods of schematic acquisition.
That being said, I have made millions of credits by crafting level 49 blue quality
armoring, mods, and augments. These entry level end-game items do not sell for a lot individually but they do sell consistently and persistently over time.
And I guarantee that when the level cap raises, whatever the level 54 stuff works out to be will sell just as well. Why? Because they are typically reasonably priced for what they offer - when an Advanced (purple) augment runs 50k+ and the blue augment runs for at most 15k (more commonly 10-11K) and you only forgo two points in each stat a given augment provides spending a LOT less for a little less is a great option. Min/maxers and hardcore raiders will disagree but that is a different argument.
The point is that crafting is not worthless and never will be worthless so long as their are players like me who craft for those not wholly interested in the top top top end, and there are buyers who are OK with equipment not necessarily being top top top end.