I would like to add I have had a single type of dot (think it was punish) do its damage as two ticks, most likely do to being applied different turns. First tick caused falter, second capture.
Now I actually am ok with that do to how you can just keep healing a character out of falter rather reliably. The real problem is that there is just no counter. On top of that there is little incentive to continue the fight and risk other characters, a simple solution would be that if your character get captured and you defeat the current enemies your downed character just gets sent back to base, if you retreat they are captured. I do also think some of the heals need tweaks, like the clerics single target heal is pretty weak, the mage heal can be so much stronger, that feels odd even if the mage heal can cause a dot, but I have abused that heal quite a bit, I use it on a prisoner meat shield who has taunted and has high defense keeping them topped off, the enemies are not downing her in one round, then on her turn the heat damage drops her to falter, but I just heal her to full as I dont care about the dot, but that multiple dots can punish that sort of thing and make them a threat is good, and you can keep track of them and keep healing up so it doesn't falter, so most of the time its enough, its just that it can sneak up on you, and that there is very little ways to stop it once the dots show up, which is why I think a way of saving them is a better option. You also could retreat if you see the dots are going to down them like that.