We had a discussion on mumble about RPPM Trinkets the other night, so I'm posting some sources about them here.
2013/02/13 10:25:00 PM - % Chance and ICD, Legendary Metagems
2013/02/15 05:10:00 AM - OnCrit Trinkets
2013/03/04 07:29:00 PM - True melee/spell haste affects RPPM, New % Chance and ICD, Legendary Metagems
2013/03/05 02:38:00 AM - Legendary Metagems
2013/03/13 04:06:00 PM - RPPM Unlucky Protection
Keep in mind that some of the above numbers may have been changed from PTR to Live, but the basic functionality should still be the same.
For more specific information about your class and your trinkets use google.

Tanks may be interested in the http://www.wowhead.com/item=95346 by the way.

For prot specs it has a 21rppm rate. The special ability hits for 280 + 75%AP, which means it scales nicely with vengeance. Furthermore the RPPM rate is affected by your haste.

Thus for a prot paladin with 133k AP from vengeance and 30% haste you would see approximately 9.1k DPS from this gem, more if any of the procs crit.

How does that weigh up against e.g. using resources for dps during a proc of the tank metagem where you can do without the active mitigation?

My active mitgation is inherent to my DPS rotation anyway.

However I will continue to run the tank meta until i get a 2nd helm and then i'll just have 2 helms with a gem in each and switch on a fight by fight basis. The tank gem is very strong, 35% uptime on a 20% dmg reduction is absurd.

I don't even see how they can justify making items this strong, especially since they're based on RNG. Going to do all kinds of mess with regard to progression race.

People also said that about the coin rolling on loot and similar shit. Who cares - as long as we get the gems and progress.

Well the coins just grant extra regular loot - not a totally OP metagem.

You could also argue that with more than one source of RNG, the chance of one guild gaining a significant advantage over another competing guild becomes smaller; no longer is 'rng' just what loot will drop, but also coins, thunderforged loot, legendary questchain progression, etc..

Also its not unusual for items with "legendary" status to offer a significant bonus to DPS/Healing etc. The daggers available from dragon soul are an example, of which we benefited due to having rogues in our raids.

FU Blizzard!