PvE you should reach arround 12k penetration. There are just some bosses and mobs, which have 18k resistances. Most have 12k or less
In PvP most guys run with arround 20k resistances, some tanky guys have more and nearly all light armor builds have less without buffs. Experienced PvPler nearly all have defending traits on 1 bar to stay tanky too. In PvP you should reach as much as you can without loosing other important stats.
PvE you should reach arround 12k penetration. There are just some bosses and mobs, which have 18k resistances. Most have 12k or less
In PvP most guys run with arround 20k resistances, some tanky guys have more and nearly all light armor builds have less without buffs. Experienced PvPler nearly all have defending traits on 1 bar to stay tanky too. In PvP you should reach as much as you can without loosing other important stats.