A 5-2 or 6-1 being the best build. Is an entirely mute question by itself. Say you wanted to first use your Dexterity. To level to level 30. Before actually gearing your character up for PvP.
1 Dexterity per level = 30 Dexterity at level 30
2 Dexterity per level = 60 Dexterity at level 30
The required amount of Dexterity needed for 95% accuracy for an Archer is 90. So, this would mean around 30 or 60 added Dexterity would be required. In order to hit the amount of Dexterity needed for an optimal character.
On the other hand, in Pvp. It really depends on how much dexterity your opponent has. So, the answer can never fully be answered for how much Dexterity is optimal. Because the answer will be different. Depending on the opponent that you are facing. Which will usually remain a ? Mark.
2 Dexterity is a much easier build to work with. Because it requires lower quality lapis in order to make work. On the other hand. A player on a Higher Budget. Could actually pull off a 6 to 1 ratio. Or, even build where all base statistics go into one statistic. While the rest is supported by Lapis. Though, this isn't always the correct path even for a rich user.
0-30 PvP BUILDS
I don't have much experience in this zone. A STR/DEX build will still be solid, but a well rounded LUC build has the ability in HM/UM to out damage a STR/DEX build at lvl 30 PvP. I would shoot for the high 400s for LUC and then try to get your DEX into the 100s. I wouldn't worry too much about STR. You will need great gear to pull off a build like this so only attempt it if you have lots of gold and are very serious about this PvP zone. Using great gear you can get your LUC in the mid 400s and your DEX into the mid 100s and you will still have some STR as well. But it requires expensive gear. If you can't afford such gear then perhaps you should stay as a STR/DEX build, shooting for maybe 150-200 DEX and the rest into STR.
This is a good rule of thumb to follow.