The major gaffe
The worst problem with this movie is Lionel Barrymore's ghastly voice.
He completely avoids any attempt to be Russian; he sounds like the ghastly John Wayne or some cornpone, hillbilly banjo-pluckin' chicken-plucker!
He was trying to stress the fact Rasputin was a rube. According to legend that's what people found profound about him. He was supposed a simple, unpretentious man of the earth not an aristocrat.
I always find odd that people hate America accents in any movie set in other countries but just assume foreigners speaking in a stagy-sounding pronounced British or Mid-Atlantic accents sounds authentic. As far as I can tell no one bothered with Russian accent.