I remember a while ago they were going to make it where you could not get the full benefits from your armors MR unless you had focus. Did this take effect? I can't find any info about it on the usual sites.
Having either Focus or Meditation enhances the effect of Mana Regeneration. The idea was to get it so that items couldn't actually
replace a skill.
As to the general usefulness of Focus? It means you can wear any armor you want, and don't have to worry about it being leather or having the Mage Armor property. It also gives you Stamina Regeneration to go with the Mana Regeneration.
Most people these days argue that Meditation is more useful, because if you're a paladin you can cast divine fury to regenerate stamina, or gulp a potion no matter who you are, and thus enjoy full stamina and the mana regeneration bonus of Meditation.
I disagree. I think that Focus can still be of good use, especially in PvM character. PvM can sometimes be about a damage over a long period of time, and the Stamina regen (at GM Focus it's the equivalent of about 10 Stamina Regen) is really, really useful. I like the Hell out of Focus on my Doom Paladin.
-Galen's player