I expected your answer to that question. Mine is... The divine law is not only to be taught, it has to be learned, explored, understood and, in a way, developed, all things that we can only do by trial and error. Where exactly is the limit? Why? What are the consequences? and how to deal with the weak ones, the aggressive ones, the always sad ones, etc. ? All this questions find, may be not a light, but at least a very meaningful shadow, from what can be seen as evil. Without it, life has no volume, God is flat, just an idol on the wall, not somebody to live with.
Your answer is interesting, but it causes some problems. Because, if God without evil were 'flat', then evil, as you explicitly say, would be necessary and it would be a kind of 'salt', making God Himself tasty! What kind of interest and taste could exist in torturing and tyrannizing people, which is the work and intention of evil?
Taken as a source of some ethical law, God (in the best case) is boring, and from that aspect, even evil can seem more interesting. A God of boredom exists only where no God exists, but our pathetic phantasms of ethical laws, etc. Real God can not cause boredom because He is infinite and personal. Imagine yourself falling down from the highest mountain; you might feel frightened or excited or anything except bored. This is how we should imagine our relationship with God. Recall the Byzantine Icons of the Revelation of Christ at Mount Thabor, where the disciples fall from the mountain, unable to endure the Beauty of Christ.
My answer to your question exists already in the papal bull comments, where I write that Eckhart grasps the action in relation with God’s will, without which nothing would exist – good or evil. Existence is by itself a praise to God, because He is the cause of all living creatures. There is no self-governing creature, a creature with mind and will, that does not willingly accept his life from God's hands. This acceptance is also a praise to God. Even an evil act as such is a praise to God, because for the person that does this act, there is a good in it, a pleasure, however sick. To enjoy the God-given life, in whatever manner and degree, is a praise to God. A 'good' person, in the sense that he doesn't hurt anyone, does his duty, good works, etc., yet unable to feel love, unable to enjoy a living and personal relationship with God, praises God less than the Devil.