TBC
Epic gear 105 to 164 Ilvl
MOP
Epic gear 476 to 580 Ilvl (with upgrades) Yes 104 item levels difference + the small amount the cloak 608 cloak provides.
The way stats add up on top of each other ensures that the next point of intellect, haste, crit and mastery is worth more than the last one. The difference between two points of spell power also increases as your stats increases. At one point, the addition of a single spell power will be worth more than all previous points of spell power combined although this number is unreachable even with 10 times more stats.
Simple example: for frost Mage bellow.
Frost bolt
1 second cast
100k damage
mastery 25% (sends an ''icicle'' for 25% of frost bolt damage)
Crit chance 20%. 100% crit damage
The average damage of 1 second casting frost bolt.
1 * 100k * 1.25 = 125k * 1.20 = 150k
+ 5% crit
1 * 100k * 1.25 * 1.25 = 156.25k = 6.25k increased dps
+ 5% mastery
1 * 100k * 1.30 * 1.20 = 156k = 6k increased dps.
+5% more casts per second.
1.05 * 100k * 1.25* 1.20 = 157.5k = 7.5k increased dps.
+5% damage
1 * 105k * 1.25 * 1.2 = 157.5k = 7.5k increased dps.
Combining all = 6.25 + 6 + 7.5 + 7.5 = 27.25k + 150k = 177.25k dps
Doing the math, a different result appears.
1.05 * 105 * 1.3 * 1.25 = 179.15625k dps. = 1.90625 higher DPS than above.
With 8 raid buffs, flask, food, potion and all raid debuffs it's easy to believe that a 476 player won't even do 1/5 of what a heroic SOO raider does. Even if their characters moves are mirrored. This difference is further emphasized when the 476 player has to reforge towards hit, whereas the 580 player may have to reforge away from it.