Both can. Shadow Warriors get 4% resist-all per slvl (capped at 75% resist all). Shadow Masters don't have a linear boost to their resistances, but Chippydip's skill calculator will tell you what their resists are.
Anyway, a slvl 10 Shadow Warrior (40% resist all) who casts a slvl 15 Fade (60% resist all) will be elementally immune, for instance. Likewise, a slvl 6 Shadow Master (42% resist all) with a slvl 15 Fade (60% resist all) will become elementally immune.
Shadow Masters have more resistance built-in at lower skill levels, but Shadow Warriors have a big advantage in that you can FORCE them to cast Fade (Masters sometimes cast BoS, instead), so they're more reliably elementally immune.