Add on to that the fact that you're going second and being hit by this. Assuming you're not immune or uber resistant, there are only 4 ways to deal with it
Triage in the same turn it's used. Keep in mind that if you mis-predict, you'll lose the card, and unless you're Life, the cards are not easy to come by
So here's the idea:
Take the scenario again. Say you're still going second and they use it. You pass without taking damage in that turn. However when it's your turn again, you start eating damage. It's basically the same as when you use a DoT when going second. It'll give the Target time to actually process what's going on. The turns would go like this. This is assuming a 1v1 match.
1) Heckhound 2) Passes (No Damage)
1) Blade 2) Blades (Damage 1)
1) Immolate 2) Heals (Damage 2)
1) Shields 2) Shields (Damage 3)
Personally I believe that this would give Players from 2nd time to react like it does Players from 1st. You can easily Triage off a DoT when you're 1st (Before it causes any major damage) because you actually get to play a card after taking damage 1, as opposed to doing it going second because you'll do it after taking Damage 2, unless you predict it.
I think, in a way, it would kind of debuff DoT in PvP, but it would make going Second less of a pain than it is
At least consider it. You could throw it in the next test realm, and if it doesn't work out, just trash it
So to paraphrase, DoT hits are all offset by 1 round, thus giving you more time to react in PvP battles where you are going second. You articulated this post well, btw.
While I can see the benefits you have in mind (surviving large one-hit KO spells in PvP), I wonder if a better solution is to give players more control over who goes first and who goes second with a turn-changing spell. If someone has time to save up 13 pips with blades, you would definitely have time to cast a turn-changing spell and place yourself in better position to defend with a Triage.
In concept, this may seem like a good idea. However, think about the fire player in this situation. How is it fair for his advantage of going first to be taken away just because its hard to deal with overtime damage? Its basically like making a fire player go second every match if he wants to use his powerful x pip spell, which isn't optimal for any school. Yes, in lower level pvp it's hard to deal with dot damage, but honestly heck hound takes full pips and blades to do good damage against good resist. There is plenty of time to prepare before the apocalypse, not to mention the fact that you can take away the damage entirely by using triage (if they aren't smart and they don't cover it with more dot damage).
Also, if you were given time to react to hits in pvp, would it really be pvp? Half of pvp is mind games, so in my opinion dot damage is fine as it is.