Stone Guardians:

Each guardian works simply. They have an AoE when they reach max energy. Before they do this AoE they will slow all units, this slow increases your resistance to their AoE but in X seconds it will freeze your whole raid causing an wipe. So you must balance this affect.

The next major mechanic is the activation: One guardian I assume will be active at the start, when within 12 yards they will 'turn on'. Once on they need to stay within 12 yards of another guardian to remain on. Only 'on' guardians can be damaged. So we will control the order that they are on. You will want to de-activate a unit before it wipes your raid, so the units will be cycled until they die.

Lastly the tile affect, the guardians will spawn crystals and interacting with them will debuff players with a Dot. This DoT can be 'drained' onto special places on the floor. When drained the tile becomes 'tapped' so to say, the raid gains 1% damage for each 'tapped' tile. This mechanic doesn't seem critical, unless healer mana is a massive problem and a 30 minute boss fight is an issue, then staking this affect will be critical.

Feng The Accursed

A 4 phase fight that will be complicated but simple. He will randomly send out shadow bolts for the duration of the encounter

Phase 1: Staff
Arcane Missiles will cause the target to have to run to the missiles to prevent massive damage, while the raid spreads out for Resonance.
Phase 2: Spear
Flaming Spear is a tank swap ability. Wildfire spark will be a simple living bomb affect that will leave fire at the explosion site. When he stands over fire he will absorb it causing him to deal 30k more damge per swing.
Phase 3: Fist
Nature Damage Shock wave, Alag style Meteor.
Phase 4: Shield (add phase)
Pull's enemy souls to him, each one that reach's him will heal him for 2-5% health. Meaning kill your soul once it leaves your body. Hunter traps, big AoE etc. And a chain lightning affect so we can't stack stack up

Now the part that I don't understand is that tanks will gain the ability to do two things.
1) Ultra-Anti-Magic-Zone: Magic area that negates boss affects
2) Reflect boss affect: Allows player to gain the boss affect when they are struck by it.

The fight to me sounds perfectly find with out this, I mean why can't the tanks just reflect the tank swap ability back on him ;P

Gara'jal the Spirit Bender

DBS meets V&T

Shadow Minions spam the raid with shadow bolts so players have to entire this 'spirit realm' to kill them so there isn't so many they cause raid wiping damage.

The other major mechanic is that every X seconds he will debuff 3 random players with the voodoo doll affect which will cause them to take 80% of the damage the tank is taking.

So basically you need to keep your spirit world team alive, so they can keep the debuff people alive, while you dps race to kill the boss. At 20% you can't re-enter the spirit world and he deals a crap ton more damage 100% haste 50% more damage. So then its just blow hero and hard race to the finish.