The short answer (to most of your questions) is it depends on what you want to accomplish—for context, I started an English MA at FU Berlin, though I abandoned it bc of the pandemic, but wish I could have stayed. The academic value of the degree is definitely less than that of a US MA (or UK or other anglophone country)—you're right to think the programs are geared towards non-native speakers (at FU Berlin, for example, a few of the requirements are more or less freshman comp/public speaking classes). The major difference, I'd say, is that course offerings are limited (think 4 grad seminars/semester at Freie, though you can also enroll at HU... in fact, if you already have some German, I'd recommend HU for its location and prestige) and class sizes can be quite large (like 25-30 students, but sometimes 35+). In my experience, too, the grad seminars don't reflect a representative overview of the discipline—they can be pretty skewed towards profs' individual interests, without much regard to even coverage of fields/eras/movements. So I'd say, if what you want is an MA in English for its own sake, it might not be a great fit. But, if you want a long term visa or a low cost credential (maybe 300 eur/semester) that non-academic employers will value and if you want to improve your German/have fun/live in a cosmopolitan city w good cost of living, healthcare, and transit links/are outgoing, it could be a great idea! From an academic standpoint, too, many departments will only be impressed if you've lived abroad and have good language skills.