You got something wrong, rangers can use debuff techs, but only the ones that can use techniks, and this does not include CASTs, like in PSO, CASTs cannot use Techniks, but they are immune to some status effects and can see traps. They can use traps, you buy them in the shop and there are burn, freeze, confusion and heal traps. CASTs have also HP regeneration, while newman have PP regeneration, and humans can use 20 materials more than the other classes to customize your stats.