yes it's designed like that on purpose to give you fomo and force you to spend plat if u actually want to craft something

last season i had over 500k pts when the event ended and i barely managed to craft a helm in the end(was aiming for a halo and i ran like crazy every day)
and also lost all of my remaining mats(same as you i had only enough cogs but every other mat was 10-15 above the number of cogs)

I posted about it on feeedback but ofcourse nothing changed(no surprise there)
here's the old feedback link if u wanna take a look: 1st cata event

given that experience and since no changes have been implemented this season i decided to not run at all
and i'm quite happy about it

i feel bad for you since all your efforts will be for nothing when the mats get deleted but hopefully you learned your lesson and you won't be wasting your time during the next iteration of this event