The drafts for sequence 4A Dwarfs At Mine and sequence 4B Dwarfs March Home From Mine are on A. Film L.A. here.
Apparently, these sequences were nearly cut from the film (Barrier p.225), in
which case the dwarfs would have been introduced in the following sequence when the animals hear their singing in the distance and hurry to watch.
One advantage of keeping them in is the fact that the diamond mine is a good and memorable set-piece. I'm not sure if the individual dwarfs get a better introduction than they would in their next appearance. They are in small groups rather than all at once, but only Dopey and to a lesser extent Doc (and Sleepy I suppose) get a chance to show their personalities. Although Grumpy, Happy, Bashful and Sneezy are introduced in close-ups with individual singing lines, nothing they do or sing indicates what types of characters they are... it was up to the animators to convey personality.
For the close-ups, Bill Roberts introduces Happy and Grumpy, Marvin Woodward introduces Bashful and Sneezy, Les Clark introduces Sleepy and Art Babbitt introduces Doc. Group shots, particularly of the four digging dwarfs, seem to have been fairly arbitrarily cast, with the same group of characters animated by Al Eugster, Marvin Woodward and Shamus Culhane.
Eugster complained that very little of his footage remained in the film. (Barrier p.224) He does have the glory of having animated the very first dwarf scene to appear in the film, but as of the washing sequence (the most recent draft sequence to have been posted up) that seems to be all. We shall see whether any more of his work survived...
Of course, it's supervising animator Fred Moore who gets the main character stuff here, with Doc inspecting the gems and Dopey as his comical assistant, who tries to amuse Doc by placing diamonds over his eyes, accidentally throws himself into the vault and hangs the key up right next to the entrance where anyone can find it!
Frank Thomas' one scene is also of these two characters: a brief shot where Doc calls "Heigh-Ho!" to the other dwarfs to let them know it's time to go home. Thomas was apparently the first of the non-supervising animators to be assigned to the dwarfs (Barrier p.212) and, as with his first assignment in scene 5A where they first meet Snow White, he seems to have been given the material that Fred Moore didn't have time to do and wasn't important enough for him to do -- like a stand-in for a leading actor!
Shamus Culhane leads the dwarfs out of the mine and into the next sequence where the dwarfs return home. Perhaps in an attempt to acquaint the audience with their individual appearances, the first scene of sequence 4B: Dwarfs March Home From The Mine was to be close-ups on each dwarf, animated by the other dwarf supervisor, Vladimir "Bill" Tytla. The scene did not survive into the film, and the numbering (it is numbered 3 but placed before scenes 1 and 2) suggest that the directors weren't sure exactly where to place it anyway. Some nice scenes by Shamus Culhane, but unfortunately the effects animator responsible for the waterfall is not identified on the draft.