Ring damage

But you CAN heal after being revived in ring2.

You are revived with 20%, ring does 5% every 1.5 seconds. So you have 4.5-6 seconds to heal. Bandage takes 5 seconds. So the only way to die to this is if you were revived juuust before the next damage tick hits. I'm not sure how long the revive timer is (and it's obviously different for lifeline), but knowing it, you could calculate when it's best to start reviving to avoid reviving the teammate just before a damage tick. But randomly, you should be able to heal in time 2/3 times (assuming you hit bandage button instantly). Anyway if 1st attempt fails, you can always try again. Also, a lifeline could immediately drop a healbot after reviving, which would guarantee successful heal (any amount of healing from it will mean an extra damage tick, giving extra 1.5 seconds).

Edit: normal revive time is 5 seconds, so the optimal time to start reviving would be <0.5 seconds before next damage tick (but not more). Best way to do it: start reviving immediately after a damage tick - this will leave 0.5 s leeway for the revived teammate to press bandage in time.

Lifeline revive is 4 seconds, which means that starting the revive immediately after tick would kill the teammate. Need to wait >0.5 sec after damage tick before starting the revive. Dropping a heal drone after revive is simpler in this case. Without healing drone, aim to start reviving roughly halfway between ticks (0.7-1 sec after tick).