I just resumed teaching TOK after a hiatus of four years, but I began teaching the course in 1987 and have taught it almost every year since then.
My two cents’ worth:
The major problem with TOK assessment is that there are only two marks—the essay and the presentation—whereas in other courses there are several. Result: one anomalous mark can really skew the final grade.
Solution: Add a short-answer TOK question to each of the exams in other subject areas.
Besides increasing the number of marks that go into the final grade for TOK, this would have the added benefit of involving all subject teachers in TOK (whereas in the overwhelming number of cases presently, DP teachers who do not teach TOK know nothing about it). This would help restore TOK to its intended role at the center of the DP curriculum.
I do not imagine that this suggestion will make it into the 2020 course update. It would take time, of course, to develop short-answer TOK questions for each subject area. But I hope that it will be seriously considered for future improvements to the programme.