As i've said it before, ret is not a dps class/spec with an agro wipe, he has however his own HoSalv wich is a very good agro dump, however it is extremely bad for him to be judging light, and he should avoid it at all costs, as it can obviously get him killed(dead dps = 0 dps, go figure).
I had holy pallies in my raid, judging JoL on raid dmging fights(naj, felmyst, etc.) and they didn't have any agro problems, it's also because they are ranged vs ret's melee(130% tank's threat at a range vs. 110% tank's threat in melee) and they are not using RF.
So the rules of judging should be like this:
1) if u have a prot pally tanking or off-tanking, he should be the only one doing JoL since he needs it and he can also efectively keep it up.
2) if you have no prot pally in raid, but u have holys and rets, then the holy pallies will be judging light, with rets judging wisdom.
Edit : Since JoL scales with raid composition, the number of melee chars, and their swing timers VS. the damage taken by these melee chars, and effectively healed up by JoL procs, it is hard if not impossible to create a spreadsheet to get TPS of it for a given raid, however you can get a number by taking the total ammount healed by JoL(from a WWS report) multiply it by the specific paladin judging it threat multiplier(2.66, if RF is up, 1.0 if it's a holy paladin w/o RF and 0.7 if it's a ret paladin with Fanaticism talent).
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