This is something that was also wrong in Logos 3, but I'm only just now mentioning it because I was hoping they fixed it in version 4.
The problem is that the MLA format for journal articles is well... not the MLA format, at least not according to the Wadsworth Handbook (5th Edition) and not according to my college policy.
For example, this is how Logos 4 (and 3) format a journal citation in "MLA":
Westminster Theological Seminary. Westminster Theological Journal Volume 1. Westminster Theological Seminary, 1938; 2005.
This is how MLA requires journal citations:
Stonehouse, N.B. "Jesus in the Hands of a Barthian: Rudolf Bultmann's Jesus in the Perspective of a Century of Criticism." Westminster Theological Journal 1.1 (1938): 1-42.
The format is:
Author's name. "Name of article." Name of journal volume number then a period and then the issue number. (Year of publication in parenthesis): pages in which the article runs.
The only thing that I'm aware of as an optional format is whether the journal name is italicized or underlined. The rest of it is standard, to my knowledge.
Perhaps there is some reason why Logos can't be programmed to fit this format, but I would at least think they could make the volume, issue number, and year conform to MLA.