You are right. I thought troopers were durasteel, but Vader's was durasteel (and Fett's before he upgraded). Stormtroopers were plastoid, so a "Fett dent" would not happen.
Blaster hits could, however, happen...
(From Wookiepedia)
"The most obvious function of the armor was protection against weapons fire and battlefield hazards. The armor, and the body glove worn beneath, were designed to disperse the energy of a blaster bolt and insulate the wearer, lessening injury. Although standard armor lacked the durability to make the wearer immune to cannon fire, it could partially deflect or disperse energy from low, medium, and high-energy blaster bolts; though the wearer may be incapacitated, survival would allow the trooper to receive advanced medical treatment that may return him to service. It also deflected stun beams, and served as excellent protection against explosions and shrapnel, thereby drastically reducing the effective casualty radius of fragmentation weapons used against troops wearing such armor."