prior to Darby, the common translation of parousia in the Bibles was coming. After Darby, a few men, here and there, began to translate parousia as presence, among them, Benjamin Wilson in the Emphatic Diaglott or whatever was his translation back in the 1800s. This was still a strongly "minority" translation. However, there were some 2nd Adventists, who, having failed again in predicting the return of Jesus, gravitated to the newer translation of parousia as presence, as in, "invisible presence," so as to explain their latest failed prediction of the return of Jesus in 1874.
BDAG is the new lexicon that was formerly BAGD. Admittedly, BDAG does say that EPIFANEIA is used as a technical term that refers to "a visible manifestation of a hidden divinity, either in the form of a personal appearance, or by some deed of power by which its presence is made known." But if you consult entry 1b (or its equivalent in the older BAGD), you will find out that the Bauer, Danker, Arndt, and Gingrich's Lexicon associates EPIFANEIA vis-à-vis the "manifestation" of Christ with a time of "appearing in judgment." One also finds information about 2 Thess. 2:8 under this lexical entry.
While this same reference work does say that PAROUSIA can denote Christ's Messianic Advent in glory when he comes to judge the world at the end of the age, it also possibly indicates that there is some type of distinction between PAROUSIA and EPIFANEIA as revealed in 2 Thess. 2:8. The EPIFANEIA seems to take place during the PAROUSIA and is actually connected with the divine meting out of judgment; PAROUSIA, however, does not seem confined to this period of divine judgment. It could be an extended period of time in which Christ rewards his servants and prepares for the day of judgment against his enemies (Matthew 24:37-39; Revelation 11:15-19).
The last sentence represents my perspective on the issue.