Here is where you list your tier bonuses and supporting results to value them so we can create a list. 2p17 http://www.wowhead.com/spell=165576 "You have a chance when you cast Chain Heal to cast a second Chain Heal at one of the targets healed." 4p17 http://www.wowhead.com/spell=167702 "When you gain Tidal Waves, you have a 8% chance to reduce the mana cost of Chain Heal by 75% for 10 sec." Tidal Waves http://www.wowhead.com/spell=51564/ "When you cast Chain Heal or Riptide, you gain the Tidal Waves effect, which reduces the cast time of your next Healing Wave by 20% or increases the critical effect chance of your next Healing Surge spell by 30%. 2 charges." 2p is an approx 4-7% chance to proc a free heal to 4-6 players, increasing in value significantly once 4p is obtained and Chain Heal is added to the rotation more. 4p is pretty much mandatory for any fights with consistent damage that can take advantage of a random chance at basically free chain heals. I'm gaining Tidal Waves every ~3-5 seconds on average because it procs from both Chain Heal and Riptide giving this seemingly small 8% chance a much higher likelihood of proccing than it may seem because Tidal Waves happens very frequently. It is possible to proc the 4p off of casting Chain Heals while its active and it refreshes the duration to max - does not extend the duration. Without 2p/4p combo it is almost more effective for me to spot heal 3-4 targets with Riptide and Wave/Surge rather than cast Chain Heal - depending on the item level and specific situation. 4p has significant interaction with Glyph of Riptide though with the changes to Riptide in Warlords and its HoT component being cut down and added to the direct heal portion of Riptide, its unlikely the glyph will see much if any use. TL;DR 4p is pretty much required for me to put out consistent AoE healing because of spell costs and regen amounts right now.