Duos - Wattson able to heal indefinitely in final ring
It appears that since Respawn changed duos from 60 to 30 players they also adjusted the ring (first ring starts already closed at the beginning of the match), and subsequently when the damage increase kicks in. Ultimately, the final ring does not do the standard damage it does in trios and allows for an exploit with Wattson and her "energized healer" upgrade to indefinitely heal in the ring.
Details: In duos the first ring starts closed. When the second ring begins closing it should do second ring level damage and close. When the third ring begins closing it should do third ring level damage and close. This process should continue and would match trios. The problem is that the ring damage increases at the end of the ring close which means that the amount of damage is offset by one level for each ring closing.
My guess is that the developers thought that they should adjust the ring damage for duos so it didn't feel like the rings were punishing so quickly given that the first ring begins closed. Personal thoughts aside, they should fix when the rings increased level of damage kicks in, or players can abuse Wattson for free wins, so long as they reach level 3 and have more syringes than another Wattson. If Respawn decides not to fix it, enjoy getting your longest win streak :)
Personal thoughts: The UI/UX effectively hid duos when it changed a couple seasons ago. There was a survey regarding UI/UX and it still was never addressed. Duos felt much better with 60 player lobbies. If the worry is that the player base is shrinking, try 40 player lobbies. This will have the same number of squads as trios.