For 4.2 patch version:
1).Reforge and Stats Priority:
a)Reforge : is all about your gameplay and requirements in arena; Can reforge everything to mastery for a better survivability or to crit for more often crits (less protection) or haste .Personally I tried all and I can say go for mastery (atm I use mastery maximized - I bought my off pvp pieces with crit or haste -reforged after to mastery). In Bg's is sweet because not all the time is a healer at your back for some help, and even in arena I finished a good number of games alone against 1 enemy player ( I'm speaking about 2v2) and worth it for extra protection. So my advice is to buy belt, boots, and wrist with haste or crit and reforge them to mastery.
b)Stats : 5% Hit ( must have) > Expertise(around 20) >Strength> 120 to 220 Spell penetration > Resilence > Mastery >Crit, Haste
2).Gemming:
!Tip! try to match colors. In cataclysm worth to take that bonus from gemming right color.
Red -Bold Inferno Ruby ( strength ), 3x Bold Chimera's Eye (only for Jewellcrafters with 500 skill)
Blue - Stormy Ocean Sapphire (for spell penetration cap +50) , Rigid Ocean Sapphire (for hit rating cap)
Yellow - Mystic Amberjewel (resilence), Quick Amberjewel (haste), Inscribed Ember Topaz (strength + crit)
Meta - Reverberating Shadowspirit Diamond (Strength + Crit)
3) Enchants: Wrist,Hands: Strength (+50 strength)
Cloak : spell penetration (+70)
Shoulder, Head : PvP enchants
Weapon: Rune of fallen crusader (better have an extra 1 with shattering rune for less disarms and a macro for swap weapons)
Legs: Dragon Scale Leg Armor (190 ap + 55 crit) or Drakehide Leg Armor (145 stam+ 55 dodge rating)
Chest: Mighty Resilence (+40 resil)
Belt: Ebonsteel Belt Buckle (+ extra gem slot)
Feet: Mastery (+50 mastery), Earthen Vitality (30 stamina+ minor run speed)
*Rings: 2x50 strength - only for Enchanters (need skill 500 if I'm not wrong)
Alex.O