Originally Posted by
Judex
Retribution is an offspec, so I might not be entirely accurate on top-tier gaming, but basicly...
EDH: it's beauty is not only how easily you can get to 30 stacks on main target, but also the fact that Seal of Righteousness applies the burn to all secondary targets with melee swings in AoE/Cleave, so it's a solid choice for all situations.
Libram: if the fight does not require you to switch a lot, or if you are overgearing the fight and you raid leader doesn't care - then it's THE 2nd triknet to go, giving you a damage buff up to 20% with max ilvl version.
UeH: Is good and solid choice. If switching is the thing needed to be done - then replace Libram with it.
Heirloom: Same as UeH but also if the demons are around. Also, you can snipe kills with HoW if you can to extend the proc.
That said, I presume there's a sly tricksters who can switch while CS'ing the same target they attacked prior to switching via Marco/target swapping, but that's some mad skills and a little loss in damage on priority target, if that's what switching is about (think Infernals on Archimonde).