I feel your pain. I had a mathematics class with an Israeli TA who didn’t know the word “coordinates.” I dropped that class very quickly.
I have also classes taught by instructors with thick accents who were wonderful. The two that immediately come to mind were both Russian, one for astronomy and one for Russian history. (WHo would’ve guessed?)
The astronomy prof had a few language issues, but he LOVED astronomy and managed make class fun, interesting, and occasionally goofy. One incident was when he using a yoyo to demonstrate orbits. He was whirling the yoyo around his head during the explanation, when the string caught on his ear. The yoyo wrapped around his head and smacked him in the forehead with an audible BONK. The class looked on in horror, trying not to laugh. The professor, on the other hand, just started cracking up, calling it a “quickly decaying orbit.” THis was a welcome contrast to my first astro prof, who was American, but dour and still bitter about his experiment being bumped off the Voyager probe. (Yeah, we got to hear the whole story about that the first class. I immediately transferred to the other section.)
My Russian history prof had been teaching this class for decades, probably using the same notes. However he still put a lot off effort into the presentation, and had a great sense of humor, so class was still interesting and pretty funny. He had fled the Soviet Union before coming to the US. At one point at my school he was the department head. The administration decided that they needed some old records, and the department no longer had them. Of ocurse the admins didn’t believe him, and continued to insist that they existed. His reaction was basically, “You want to play bureaucratic games? I am from the Soivet Union. I KNOW bureaucracy.” So he told the admins that they had to submit their request on department form 1H-1A. They duly submitted the form, at which point they were informed that 1H-1A had been superseded by a new form, 1H-2A. Everytime they submitted the new form, there was a new one. Eventually they gave up.
I also had a linguistics professor who sucked. He was American, and apparently quite the researcher, but he obviously considered the class a waste of his precious time. He just didn’t give a damn, and it made that class boring and a general pain in the ass. Thankfully my professor for historical linguistics and almost the complete opposite; I still have fond memories of that class.
My point is (what the hell is my point? Oh yeah.) that accents can be a real pain in the ass, but the instructor’s attitude towards class is a bigger factor in how good it will be. IMHO, YMMV, and all the jazz.