It depends on how expensive they are.
For example, if you doubled the combine cost of LW (so the item goes from 2.3k to ~3.2k) and took away the +5 AD bonus, it would still be vital for defeating armour stacking enemies, but would be highly inefficient against enemies who invested in health or offensive stats instead.
Part of the problem with LW at the moment is that it's pretty cost-effective even if the enemy has only base armour. It's possible that in S3 that may no longer be the case.
I mean, stacking ArPen or abusing % -> flat could turn out to be horribly OP in S3 (even more so than now!), but it all depends on the numbers.