Originally Posted by
WarTotem
Assuming it still works as it did in WotLK, it's 2%, reduced multiplicatively.
Back then I usually ran an alt group with a bear as second tank half the time, so I could afford to grab a separate helm just for meta and use it on fights like twin valks, Sindy,...
Although I only have a healer perspective, I'ld assume that fights such as Maloriak, Nefarion, Elemental Council, Al'Akir are all good fights to use such a meta, as they provide reduction on bursts or healing-intensive moments.