These rings were added, one can assume, over a lot of protest and QQing by tanks and healers. While the two rings currently in the game can be used by both roles in some situations, they are by no means what healers or tanks would be looking for.
As a Protection Warrior I'm looking forward to this change going live. I'll have to fork over another 8,000g or so, but such is the price of epics.
A closer look at the rings and their stats after the break.
The loop is nice for those casters who want mana regen (Warlocks, har har har). The spell power increase of 59 points is equal to that of the Signet of the Kirin Tor, however this ring is lacking the direct increase to critical strike and haste that the Signet has. Expect healers to be happy with this one.
The Ring of the Kirin Tor is a good tanking ring. Some might like it for PvP as well. High stamina (+75) and high strength (+50) make it ideal for a Protection Warrior. The expertise and critical strike are icing on the cake (although it should be noted that I tend to stack critical strike after my other stats are at acceptable levels). Overall this ring is a much better tanking ring than the Band of the Kirin Tor.