Grift Score equates to your hero achieving the best time and rift level - solo,2, 3 and 4 player groups are added together for each hero.
Hero Power is a site based formula used to assess the heroes full potential ingame - this includes everything from paragon levels, elemental + skill based damage, elite dmg, toughness, cooldown + cost reducation, crowd control and healing.
DPS (Burst) listed here is the total unbuffed damage from your items multiplied by your best total Elemental percentage * Elite Damage * best Skill percentage (DPS graphs and calculators now use this as baseline).
EHP (toughness) represents the heroes total unbuffed mitigation which includes simulating block effectiveness, armour, resistances and dodge from items.
CDR% is the total cooldown reduction - and is weighted so that you gain more the closer you get to 100% (ie. 50% = 2x Hero Power, 66.6% = 3x Hero Power).