If they really do intend to tie Rebuild story into that of NGE, then I'll probably have to rewatch NGE to comprehend the new plot. It's an anime series with a plot and characters that are very much worth rewatching anyway, so no problem here.
As for Mari, I like her, but I can understand why she is disliked. Rebuild 2 was simply too darn short for the amount of plot it covered, and Mari hogged precious screen time that could have been used to flesh out other characters, particularly Asuka. I really would have preferred Gainax to cut down the average budget per scene to make the movie around 150 minutes long rather than 110. The film wouldn't have looked as utterly breathtaking as it ended up, but it would have been much better paced.
The two reasons I like Mari are
1. Because she's super sexy.
2. Because her crazy personality is fun to watch.
Both reasons are shallow, but they still rescue her from being an undesirable character in my eyes. Still, not everyone will appreciate her qualities as much as I do, and it does say something about the value of a character in a story when the audience's opinion on her depends on how sexy and crazy they find her.
Is Mari a character? Yeah, but not a main character, and maybe not even a secondary character. She might acquire a more pivotal role in later films, but right now she stands out as little more than a tertiary character, similar to Patrick from Gundam 00, and Kiyal from Gurren Lagann. And I like her for what she is.
