Q:
Best WvW and Pve build for mesmer ?
Well what are you doing in WvW? If you’re roaming, then I’m a fan of the 2/4/6/2/0 PU build for survivability. For zergs I’m much less knowledgeable as to what people need mesmers for.
For WvW any variation of PU (rabid or zerker gear are probably the most effective here) is the clear winner if you plan on roaming at all. If you just want to join a zerg and tag things, you should reroll to elementalist since mesmers scrape the bottom of the tagging barrel.
Little is more survivable than rabid (maybe a bit of dire in there too) PU mesmer, 3k armor and 20k+ health and 2k condition damage with food/stacks. Staff+traveler runes basically mean you will only fight when you want to, even thieves and warriors will have trouble engaging you against your will.
For PvE there is no variation at all, just get full zerker gear and change your traits depending on what your group needs most, usually reflects.