In Mark 1:44, why did Jesus command the man he cured of leprosy to offer "sacrifices" that Moses commanded for his cleansing as a testimony to them?See that you don't tell this to anyone. But go, show yourself to the priest and offer the sacrifices that Moses commanded for your cleansing, as a testimony to them.In reading this verse, it is clear that Jesus specifies that it was Moses and not his Father who commanded the Jews to offer sacrifices for cleansing. But Jesus is against sacrifice! So one would ask, why? Why did Jesus command/encourage the leper whom he healed to continue in performing a sacrifice? Jesus states "as a testimony to them". Perhaps, this was the reason he commanded the leper to perform the sacrifice? But why would Jesus choose to show testimony of God's cleansing by using men's terms (sacrifice) instead of the Father's terms (mercy)? For surely this is why the leper was healed...the Father's mercy on him! Surely Jesus was using this leper to show the high priests that it is mercy and not sacrifice that the Father desires, and thus the leper was healed before performing his sacrifice in front of the high priests?
The leper was forced to live under the restrictions of the Law until the priest certified him as cleansed. He could not return to a normal life in his home or with his family or friends. The relevant law is in Leviticus:
 "The leper who has the disease shall wear torn clothes and let the hair of his head hang loose, and he shall cover his upper lip and cry, `Unclean, unclean.'The process of certification, that included the offering of a sacrifice, is fully described in Leviticus 14. So, Jesus' command to submit to this procedure was itself an act of mercy, for only thereby could the man return to a normal life.
 He shall remain unclean as long as he has the disease; he is unclean; he shall dwell alone in a habitation outside the camp.
You are very observant in noting that Jesus specified that it was Moses, and not the Father, who had instituted this procedure (command). But the fact of life was that the man must continue to be ostracized from human contact until the priest had certified him to be cleansed of leprosy.
Therefore, this does not at all indicate that Jesus affirmed the sacrificial system of the Jews. It is only more evidence of his emphasis on mercy, which you are correctly putting to the front. Both the healing and the instruction to offer the sacrifice were acts of mercy.
You see also why he used the phrase, as a testimony to them. The certification of his cleansing by the priest was the necessary testimony to the people that he was indeed cleansed and could return to living a normal life with his family and friends. I don't think that your suggestion of the order of events is significant -- i.e., mercy before the sacrifice, since in any case he must be clean before the priest would accept him into the process of certification of his cleansing, and both the cleansing and the procedure were applications of mercy.