Welcome! :) I recommend you to re-render done videos inside the "handbrake" program. (google for it). It makes the file size less heavy, so it load faster for ous on D.tube.

The creator of D.tube said this in a post, that handbrake makes it easier for d.tube to load peoples content. Youtube has this feature, but dtube hasnt yet I think (unless if they updated without I know).

handbrake = re-render videos in same format, but less heavy and dont lose quality.