But if you're going to continue this bizarre episode of straining at gnats and swallowing camels, you might compare the narratives in Mark 16 and Matthew 28, where Mark states that the women were "bewildered and afraid", whereas Matthew also has the words "but joyful". The fact that the women were filled with joy is quite obviously the central idea in the significance of the Resurrection for Christians, but Mark leaves it out. According to your ideas on the order of the gospels, Mark would have had to deliberately suppress it. Unlikely, I think.
I can't answer this point yet, but I will say this: like Luke, Mark says that the women entered the tomb. Matthew doesn't explicitly say that they entered it, though he implies that they saw where the body had been.
Accordingly, in Mark 16:8 the women 'went out' from the tomb, and in Matthew they 'went away' from the tomb
So if Matthew was dependent on Mark, why this difference, why doesn't he describe them going in and going out of the tomb. But if Mark is dependent on Matthew and Luke, then this is evident in the way he has conflated them, taking from Luke that they went in (and subsequently went out), and from Matthew that they went away (but changing it to 'went out').
In other words, Mark writes 'exelthousai': this being a conflation of Luke's reference to the women entering the tomb, and of Matthew's word for going from the tomb, 'apelthousai'.
It is unlikely that if Luke and Matthew used Mark, Luke would chose to include the women going into the tomb, and not chose to include Mark's verb erchomai, while Matthew would chose the opposite.
Mark's omission of the women's joy is puzzling, but not indicative of Markan priority.