Greeetings,

We apologize for the delay in responding to your question.

(a) The Gemara's phraseaology of "Rav Yosef Amar" as opposed to "Amar Rav Yosef" implies that Rav Yosef is arguing with the previuous statement (see, for example, Tosfos to Bava Kama 9b, DH Rav Huna). Hence the first statement was probably made by Rabah and not Rava, since Rabah is usually the one who argues with Rav Yosef.

(b) Rashi explains that Rabah is deriving his comment from the words "ba'Yom ha'Hu," which imply that Hash-m hides His face from us, as it were, by day but not by night. Rashi explains that at night, Hash-m shows us in a dream what will happen in order that we pray for mercy. It would seem that according to Rashi, Rabah is explaining that this is an additional punishment -- that even though Hash-m is "Mastir Panim," meaning that He does not answer our prayers as Rashi explains (DH Eino me'Hen), nevertheless He shows us the terrible decrees that are about to befall us so that we should be frightened and pray, and when we pray He does not answer.

Rav Yosef argues and says that if Hash-m reveals to us the upcoming tribulations in a dream, He certainly intends to answer our prayers when we pray that He should protect us. He expresses this by saying "Yado Netuyah Aleinu," meaning that His hand is outstretched to shield us from the Tzaros, and that is why He reveals them to us in a dream.

According to Rav Yosef, what one sees in a dream is not included in the Hester Panim.

This appears to be the Gemara's explanation according to Rashi.

(c) If not for Rashi's comment, we might have explained the Gemara somewhat differently. Rabah and Rav Yosef are not arguing about the inference from "ba'Yom," but rather about the inference from "Haster Panai ." According to Rabah, "Panai" refers to what a person perceives of Hash-m during his waking hours. As we find by Moshe Rabeinu, with whom Hash-m spoke while he was awake, the Torah describes his relationship with Hash-m as "Panim El Panim." The inference from the verse is that although during our waking hours Hash-m hides Himself from us, nevertheless while we are asleep Hash-m reveals Himself in order that we will pray and be saved from the Tzaros and oppression.

Rav Yosef learns that the Torah uses the word "Panai" to imply that Hash-m hides only His face, but His arm is still outstretched and there to protect us, as if He is hiding behind a curtain and protecting us with His arm. That is to say that Hash-m saves us nowadays through Nisim Nistarim that appear to be part of the natural order, and He does not show His face -- meaning that His presence is not made evident through open miracles.

M. Kornfeld