T10 set bonuses

Shaman

•Item - Shaman T10 Restoration 2P Bonus - Your Riptide spell grants 20% spell haste for your next spellcast.
•Item - Shaman T10 Restoration 4P Bonus - Your Chain Heal critical strikes cause the target to heal for 25% of the healed amount over until cancelled.
•Item - Shaman T10 Elemental 2P Bonus - Your Lightning Bolt spell reduces the remaining cooldown on your Elemental Mastery talent by 1 sec.
•Item - Shaman T10 Elemental 4P Bonus - The cooldown on your Lava Burst ability is reduced by 15 sec.
•Item - Shaman T10 Enhancement 2P Bonus - When you activate your Shamanistic Rage ability you also deal 12% additional damage for 15 sec.
•Item - Shaman T10 Enhancement 4P Bonus - Each time the beneficial effect of your Maelstrom Weapon talent reaches 5 charges, you have a 15% chance to gain 20% attack power for 10 sec.

Lets look at the 2 pc first: an additional 12% damage for 15 seconds every minute. Or an extra 12% damage 25% of the time, which averages out to 3% extra damage. At 7k dps thats 210dps. Seems pretty nice to me.

The 4 pc set is a bit trickier to do napkin math on. Due to RNG it can take anywhere from 2 seconds to 20 seconds to gain 5 charges. Lets say on average its 6 seconds. I doubt the procs would stack, but the duration is longer than the average chance to proc, so lets say up time is 15% lets use 6000 as an average AP in raid. So the bonus is 1200ap 15% of the time or 180 ap average. 6000 ap is probably a bit low in an optimized raid, so the better your buffs the better this bonus is. I think i need someone a bit smarter than I am to work out the value of the 4 pc. :)