Expose weakness on what roles?

So since the new mastery came out I've been kind of curious, I believe it's mainly a support mastery but your input would be helpful. Generally melee champions take double edged sword if they're fighters or assassins, and before the 6.4 patch it was either that option or feast. Thinking about this, feast doesn't do that much, you get a little bit more sustain but if you're losing lane hard it won't even matter. As well for the melee champs who aren't meant to do damage, wouldn't it be better to take exposed weakness over double edged sword (On champs like rammus or shen who are meant to just tank and not really be the main source of damage)? While champs like warwick or shyvana would still take double edged sword cuz they're late game damage building tanky is still decent.

Basically, all the midlaners, adcs and tanks, shouldn't they just take expose weakness since having feast doesn't do too much? I could be underestimating its strength though but idk, opinions would be appreciated.