Hi, I have taken Verbling lessons from about twenty tutors, (hundreds and hundreds of lessons) I often see errors in the English version. Usually it is a very small thing, like mistakes I would make in French. (C1)
I always feel shy about correcting my teachers, and especially people I never took lessons from, though.
For me, I do not need tutors who speak perfect English, or even speak ANY English, but since it is your marketing material, and there are total beginners here, perhaps having someone look it over is a good idea?
There are so many who speak 4-5-6+ languages here, and I have mad respect for that. Would you want someone (a stranger?) to tell you? Or would that person be kind of a jerk?