If it's in ultimate, as high as you can get it, period. The monsters in EP2 ultimate have stupid high evade.
If you're using a HU character, (and maybe even some RAs!)expect alot of misses if you don't have some hit weapons, arm units or a mag with sufficient dex on it.
Those Gibbons and Zol Gibbons are probably the worst in EP2. (the orangutan looking monsters)
They are VERY hard to hit without some stuff to raise ATA with, they move around alot too making it even harder to hit them.