Again, we note that “psalm of Asaph” is colloquial for the man and all his descendants, all who held his office following him. It matters here because this is almost surely a psalm from the Assyrian conquest of Samaria and the Northern Kingdom. The psalmist names Ephraim, Benjamin and Manasseh as shorthand for most of what was left when Assyria invaded and took them away (typically dated as 722 BC).
Nowhere else does the phrase “Shepherd of Israel” appear, but here it reaffirms that Jehovah is the ultimate Pastor of the whole nation, though by this time “Israel” typically refers to the northern tribes only. Asaph calls on God to come and save them. Sadly, He did not, for reasons adequately explained by various prophets. But while it remained a possibility, the psalmist performs his divine duty calling out to God on behalf of the Covenant People, regardless how they may have strayed.
Verse 3 is rather like an irregular refrain repeated in 7 and 19. We can see what a deep and passionate plea this is that the author forgoes the niceties of symmetry. This is a tragedy that affects the whole nation. All they know is tears, and it was embarrassing how the north and south often were at war. Again the refrain calls for restoration.
Then he launches into an extended parable of Israel as a vine, a common image used in other Old Testament books. This vine was transplanted from Egypt. The land was cleared of whatever was there and the vine prospered in its place, spreading far and wide. Now the protecting hedge of God’s favor was gone; everyone and everything ate their fill down to the very roots. Without rescue, there would be nothing left to regrow.
What was all this vast investment God made only to let it go to waste? But when God’s face turns away, there can be no hope. Is there nothing left worthy of saving? If God returns His favor once more, it can recover and be that strong servant of God that it once was. One more chance, Lord!
The psalmist closes with the final refrain calling on God to save what is left.