Rarely does the literal translation fit into the meter of the original text. In this hymn, it happens at least twice:
It seems when this happens the translator's work is a little easier, so I am not sure why one would tinker with the line "Er hilft..."
LSB (rhythmic) wins with the literal sense once again.
Heading back to Scripture, LSB (isorhythmic) is more closely aligned with verse 9b of the King James Version (1611). The German comes text comes from verse 5b:
The text from hymntime.com uses more imagery and less literalness, but it is fairly close when you get right down to it.
Omar Westendorf's translation seems to be a fish-out-of-water, though. He goes with "protector" instead of "helper." It is further away from the literal translation, but the imagery in this instance seems to work.
Westendorf's use of "staff and rod," though, is more closely related to Psalm 23 than Psalm 46.
In Psalm 46, God is breaking the rod (or spear) of His enemies. In Psalm 23, God uses His rod (more of a long stick in this instance) to help comfort us.
Westendorf's translation here is out of context. Where this portion of Psalm 46 is crushing, the Psalm 23 reference is comforting.
Ein Feste Burg is a paraphrase of Psalm 46, not Psalm 23. The two aren't necessarily meant to be combined. Take this paraphrase of Psalm 23 from LSB 710:
If you combine this section with Psalm 46, you might get this:
Psalm 46 shouldn't be softened by Psalm 23. Likewise Psalm 23 shouldn't be sharpened with Psalm 46. These two Psalms serve different purposes.
In summary, most of the translations are faithful to Psalm 46 but differ here and there from the literal translation. Westendorf, by veering off to Psalm 23, changes the scope of the literal meaning as well as the context of the passage.