So much disinformation... much wow. I give up. seriously.
I was about to do the same test done by Moriala to confirm the thesis (... no wait, it's not a thesis, it's a FACT....) that HC doesn't affect the damage of other people but only pom's.
So thanks Mori, you saved me some work
HC works like this (I'm not making this up, I'm just reading the tooltip):
1) gives 1650 protection (elemental and holy)
2) gives 3300 protection (unholy)
3) resets the cooldown on condemnation giving a free holy storm side effect
4) enhances passively divine halo by 50%
5) puts a +60% poison (which is physical damage, better to state it since some geniuses keep believing that poison damage is elemental...yes I heard that too, sadly)
6) put the hc effect on 12 people around the healer (maximum 3 meters) which makes them DO additional holy damage which is counted as pom damage.
HC is dangerous for the pom only if used without caution as it is a huge self burst bomb. IT does not give any damage buff whatsoever to the rest of the raid-group.
Couple random free notions:
-When back in the days people in t3 used to say "poms rotate hc on louhi in the beginning phase to buff necro pets" it was just a way to say that THRU Holy cleansing, the pom was able to deal more damage because the necro pets were buffed by it. Still, the damage was dealt by pom and does not contribute to other's hate at all. This is applied to every similiar circumstance (example: adds in yothians).
-If people randomly die in t2 imp, it's cause the imp (black funny transparent guy) is untanked, maybe cause they overaggroed on athyr bast, maybe cause that was a bad day for him since he broke up with his girlfriend or whatever else...but for sure It's not because of hc.
Those are facts.
Now, unless you want me to believe my grandfather was a pinball cause he had 3 balls, then please stop giving bad informations.