Imo,not really.
Comparing your logs even from a static boss (patchwerk like) with a sim,is not that usefull.
You have always to consider that doing a simulation of 1200 x 5 minute fights and comparing it to a single 5 minute log is too much rng dependant.
Instead of just comparing the percentage sources of damage,i'll suggest you to compare the percentage of abilities casted.
Then,maybe,try to do some maths.

Can't be that, you're easily hit capped against anything +1 or +2 levels.

Impressive testing, however do you know of any other sources that also point out a hidden 1 second icd? I haven't been able to dig this up anywhere else.

Our test was only 2 Holy Paladins, 1 Prot Paladin and our DK. So due to this, the number of adds never really got INSANE and stopped I'd have to guess around 20-30 adds. Not enough to log some absurd DPS numbers, but enough to get an idea of the DK mechanics easily.

The ICD is pretty apparent looking at the logs, like I say, almost identical numbers for Blood Plague, Frost Fever and Wandering Plague hits. This indicates that every 3 seconds, each disease ticks on every target and ONE Wandering Plague procs on every target. The ICD might be 3 seconds and not 1, there's not a real easy way to tell and I'm not sure if he was using Glyph of Disease (though I assume not). Without GoD, your combat should look something like this:

0.0s: Blood Plague applied to target 1
1.5s: Frost Fever applied to target 1
3.0s: Pestilence both to all targets, Blood Plague ticks for the first time on target 1.
4.5s: Frost Fever ticks for the first time on target 1.
6.0s: ALL Diseases tick simultaneously on all adds for the first time. Blood Plague ticks for the second time on target 1.

So basically everything is synced up other than Frost Fever on your first target. If the ICD was 1 second, then I should have seen a decent handful of additional Wandering procs due to that one single de-synced Frost Fever. However, like I said, the number of Disease ticks and Wandering Procs were nearly identical.

When I mentioned capping out, that was simply OUR DK capping out in that very specific circumstance with that exact number of adds. Diseases and Pestilence have no cap so the sky is the limit on those, Wandering Plague and DnD seem to be AE capped which means that once your targets pass the 10 mark, you're not doing any more damage with those abilities, it's just spreading out over more targets.

Paladin Severed Essences by the way do indeed just mainly sit there healing, but they also have an aura which restores 3% of all targets' HP every tick...so basically once you get 20+ Paladin adds going, you'll never out DPS them because they're passively healing something like 90,000 HPS. Anyway, bring more Paladins and you can EASILY test this much further. The adds cap out seemingly based on how many people are fighting them, so with only 4 people there, I don't think we really saw more than 20. If you had 20 Holy Paladins, 4 Prot Paladins and 1 DK...then we'd be talking some serious business.

This actually DOES all have some interesting implications that need further testing. If the Wandering Plague ICD is indeed 1 second, and that slightly de-synced Frost Fever has a chance to proc WP separately, then it means Glyph of Disease is almost a guaranteed LOSS of DPS on heavy AoE fights.