We might not share the same views on this episode but its ok. This post is not meant to bash or berate anyone be it the actors or those on the forum. My judgement is solely based on my analysis of the characters within the show. There are some many ways in which I see the episode, but I won't any post much so as to keep it to a minimum.
In my opinion, Davina and Marcel should be included as some of the main contributors of everything that has happened so far. Others include the witches, all Mikaelson members, Lucien, Arora etc. Everyone has contributed in some way or form, and this cannot be overlooked.
Firstly, she gave Marcel the power to suppress the witches (s1), this lead to Jane-Anne Devereaux using Hayley as a method to get Klaus to New Orleans. If she hadn't done so and allowed herself to be sacrificed as an harvest witch (she resurrection was guaranteed - all the harvest witches came back to life) then Klaus would've been in Mystic Falls probably chasing Caroline & all the chaos in NOLA wouldn't happen.
Plus Marcel knew that his alliance would get Davina in trouble yet he allowed her to help suppress the witches. Not to mention, she is the reason Cami(de-compelling her which made her stay in NOLA) and Finn(trapping him in his body) are dead.
She had already made her bed with the ancestors, so they would kill her 1 way or another. Not only did she cause them to get suppressed by Marcel, but she also killed them ( sophie devereaux's best friend - can't remember her name right now - and her companions in s1, arranged for their murder (Kara Nguyen) and used her regent power to bring back Kol when she vowed to use it to destroy the Mikaelson family.
Her demise was inevitable as long as the witches were after her. Remember hadn't she broken Klaus' sire line then Lucien wouldn't have killed Cami/Finn plus he wouldn't have been able to be transformed in "An Upgrade of an Original". Davina's major problem is her impulsivity. She always sticks her nose in things that din't concern her eg Kol/Finn, and always starts waging war against Klaus.
Marcel basically knows that when it comes to the Mikaelsons, family always comes first. They will abide by their "Always and Forever" no matter the personal.conflicts they have with each other. It has practically been this way for 1000 years. So it strikes me to see that he has fully placed his trust in them when he knows that they'll sacrifice anyone for family. Look at Celeste, Gia all their endless lovers. Family is the main priority over friends and lovers. Gosh I'm so glad that Hayley has made it into the family list.
I sorta get why Marcel is that upset. I mean his adopted daughter has literally gone for good. But Davina's death allowed Rebekah the one he claims to love, Klaus and Hayley to live who have been his family (except Hayley) far longer that Davina. Davina may be his daughter but Klaus is basically his father.. Its ironic that he says that everything the Mikaelsons touched they destroyed, when he basically destroyed the last drop of humanity Klaus had a century. Klaus has said it himself that when Mikael destroyed New Orleans he lost his compassion and humanity. Lets not forget that it was Marcel who made that deal with Mikael in exchange for all of New Orleans. He even gave up Rebekah for the place. Speaking of touching and destroying, his affiliation with Davina in s1 marked her doom...and his friends such as Diego, the musician and othe who died when he signed them up for war against Klaus. Also he has mercilessly executed many NOLA witches so he is not all that innocent.
Somewhere I pity Davina for the way in which she died. She didn't deserve to get her soul vanished like that, but we alI know about loopholes. I'm surprised Freya decided to help her (given she triggered Finn's death), which off course was short-lived and temporary. I don't believe for a sec that Elijah and Freya didn't have a choice because she could've channel Van who was regent and use his power to reverse Lucien. Then Davina would still be in the circle.
Post is getting too long
P.S. why was she thanking Marcel. He ia not a witch is definitely not the one who pulled her out of the ancestral plane.