How you could patch out the lifeline camping outside the ring strategy

I think the way to go would be to add an increased cast time based on how much hp you have healed in the last 20 seconds. If you have healed more than 200hp, suddenly everything takes twice as long to use (hp only, not shields). If you have healed more than 400, or you dont take a 15-20 second break between heals, it goes to 3x base cast time. Then 4x. By that time, if you have been healing just outside the small circle, the other team is inside the circle, you will be dead before the circle has a chance to kill them. This would have a minimal impact on any other circumstances, because unless you are healspamming where else would you be using medkits back to back? Earlier zones are a non issue since you can wait about a minute between uses until you get to a zone size where its absolutely reasonable to expect you to get inside within 2 medkit uses.

Edit: gonna throw in another alternative backing up old mates damage ramp suggestion. Set timers based on which round it is, for the first round 2 mins, second round 1 min etc reducing to 10 seconds when the zone is at its second smallest. After that time, the damage doubles. When the same time goes up again (4 mins from round 1), it doubles AGAIN (now doing 4x standard damage for that round). A competent team will 100% find the straggler INSIDE the second last zone, forcing them to sit outside that zone to make the strategy work, but within 30 seconds it will be absolutely impossible to outheal.