Forgive me if this has already been figured out.
I've read a few places questioning why Deathmarks would want to deep strike. The answer is because of the Hunters from Hyperspace rule. The rule states that they choose their unit on the battlefield to mark when the Deathmarks are deployed. If you go first (or made to go first), then your opponent has no units on the table to choose to mark, hence they would not get the chance to take advantage of the rule.
If anyone else has something to add, please let me know.