Armor doesn't stop one from getting knocked down from a physical attack. It just keeps one from being pieced by blades and bullets. Blunt force trama can be made non-fatal by the armor, but it will still likely knock you down.
The stormtroopers on Endor were knocked over by primative weapons used by the Ewoks, but if you look, you might notice that most were not killed by that, but when jumped and basically hacked and beated by lots of Ewoks each. Arrows seemed to only work against scout troopers who had less armor and the unarmored officers. The main thing the Ewoks achieved at the start was mass confusion allowing the Rebel to regain their weapons and start shooting Imperials. The tide didn't seem to turn until Chewbacca managed to gain control of an AT-ST and the Ewok traps started taking out the Imperial speeder bikes and AT-STs. The stormtroopers are killed either via Rebel basters, AT-ST fire, or blunt force trama via being mobbed by several Ewoks at once. All other instances or rocks seem to only knock the trooper on their butts to allow other Ewoks to mob them. Arrows seem to not do much unless it hits in the gaps in the armor. The body glove not providing protection against pointy things.
One might note though that a blaster shot Stormtrooper might not be dead. Going by Rebels, there are troopers that have been shot or being very close to massive explosions that have survived to be shot again or been in another explosion. An example of those this is the TIE depot on Lothol. Sabine attacks and blows up some TIEs at the depot in the preview clips that introduce the characters before the season started. Several troopers were taken down at point blank range from her detonators. Late in the first season, she attacks that depot again as a distraction. The troopers remember her and when she leaves them another detonator, they remember that as well ("not again"). So it is possible that stormtrooper armor is more effective than we give it credit. Han Solo blaster is suppose to be a "heavy blaster pistol", so like taking a magnum to body armor. The Stormtrooper blasters are carbines, so they are heavier weapons a well. The regular blasters might not actually kill a trooper (still might knock him on his butt). Not sure about Leia's long gun in both Star Wars and Return of the Jedi.