So what are these items for? My interpretation is that they're largely to help your alts level, and to give you something to do with badges if you have too many on your mains. Although the stats do scale down when you equip them on lower-level characters, they're still quite powerful items, on par blues. And here's one thing that's reinforcing that impression: I've found four Heirloom shoulders so far that give +10% experience from killing monsters. This is a great idea. You know that anyone who has these shoulders has at least one character at level 80, so why not let them level 5% faster? (5% is based on an estimate of half of one's experience being from quests and half from mobs.)
There seems to be a set of +10% experience shoulders suitable for every class and spec. Armor type (leather/mail/plate) will vary as appropriate for the character you equip them on, as far as I can make out.
- Tattered Dreadmist Mantle
- Preened Ironfeather Shoulders
- Stained Shadowcraft Spaulders
- Champion Herod's Shoulder
- Mystical Pauldrons of the Elements
- Polished Spaulders of Valor
It's really nice to see old models return. I expect we'll see very many of these shoulders on sub-80 characters in LK. I'm excited to be able to level my characters that much faster; I've spent more than enough time in Azeroth at this point. As Zach pointed out, Heirloom gear puts the emphasis when leveling on getting levels; it discourages going into dungeons and pursuing drops. Not that I do that these days anyway.