Yes, Marian is a viable option to swap in. You won't get the extra damage procs caused by Enya's support skill so the overall time will be a bit slower. For my team, M0 Marian is 5 seconds slower. Just hold her off until you run both bosses cause you never know if Marian may be needed to fight against Pi Purified. I'll make video with Marian in the team and one without Marian for Pi when I'm able to.