If you die without weakness on you the moment of your death, you will be revived without weakness being applied.
If you die with the first stage of weakness on you the moment of your death, you will be revived with the same weakness stage and its timer reset to its maximum.
If you die with the second stage of weakness on you the moment of your death, you will be revived with the same weakness stage and its timer reset to its maximum.

In short terms: the more you die, the more you're screwed. But a team with members dying without an already applied weakness will be revived to their full potential.
This is to allow smart uses of Healer LB3 (like in A4S), or to make a comeback after a small mistake, while denying absurd comebacks of people dying again and again.