As the title says, not sure whether this is intentional or not, but DoTs seem to deal damage based on the resistances you have at the moment they are applied, and they ignore any changes to your resists after that point. This is best seen on characters using Blood of Dreeg (with Aspect of the Guardian). If you take a poison DoT when BoD is down and your acid resist is low to negative, then apply BoD, your health will still drain at breakneck pace despite your resist now being comfortably 80 with overcap. The damage of a DoT, once applied, does not seem to update. This would indicate the same applies to other sources of resist, making effects such as Resilience, Serenity and other circuit breakers less effective at mitigating DoT damage (particularly Trauma since most of the time players are not capped on physical).
It will similarly apply to enemies. If you’re playing a DoT-heavy or even DoT-focused build, you should see dramatically different results when you apply your DoT after rr. Normally that would be the order of operations anyway, but there are some proc RRs such as Rumor, Voidheart, Combustion Band etc. that may not be under your control. This will make DoT builds perform worse than they should, and somewhat reduces the value of these rr effects for DoT builds unless they meticulously reapply their DoTs (and then there’s the question of if the DoT damage will update with the new resists, or if it will simply extend the duration of the original, weaker DoT).