Nah, Kasumi is still more popular than Marie Rose (and hardly someone will change it): in these days you see more showcasing of Marie just because, contrarily to Kasumi, she is part of the new additions to the series and can be used for promoting it (contrarily to Kasumi that is literally free for everyone with the core versions).
They don't use Honoka because, even if the real main female of Last Round until new DLC charas, it's still too much early for realizing if she will be popular or less for the fanbase (even if I think that everyone can imagine what will be the answer XD)
If they want to promote the game in Japan with moe (which seems to work), I say go big or go home. Honoka and Marie on the cover doing their tag win pose.
I don't understand why, after putting a majority of the characters on 5 and 5U, they stick Kasumi+1 new character on LR's covers.
But it's not a matter of moe, like I said they selected these characters on the basis of what are the most popular ones, and so what jipotehtically the JPN fans of DOA would love to get in a cover.
What you said about Honoka make sense if they would have decided to promote the game through the showcasing of at least one new additions, however this wasn't the case (even for the West cover too).
By the way be sure that Honoka and Raidou will be included in the back of the cover. Also, apparently the DLC characters of DoA5U (MR and Phase included) are treated as new characters of LR judging from the JPN trailer.
In the end it's all a matter if you want promote the game with a cover that has a focus on your plot,on your new contents, on the popularity of your characters.
The last two didn't feel like they were pandering to a specific audience (well, Kasumi had a panty flash for 5U in Japan but it wasn't the focus of the cover) but now the Japanese one definitely is.
Marie being somewhere on the cover if they did another group shot one absolutely makes sense but her being so important she's one of two characters? Doesn't seem right
The fact is that Japanese love do popularity pool in their works, overall because they allow to the tastes of the people to influence commercial works. If they realize that people want see something, in the limits of the possible they will try to appeal the majority of their fanbase (inside certain limits, off course: Marie Rose will get a big room in DoA6...
but hardly she could ever be able to be part of the main events of the plot involving the ninja).
Btw in part this happened also with the previous covers, indeed it wasn't a case that you saw Kasumi and Ayane (that was the 2nd more popular chara at that time, but that in DoA5 hasn't a more important role than Hayate) in front of everyone.
However personally I agree with you and I also prefer give the priority to the plot of the game or anyway to something that make sense inside the work, rather than for the audience of it (that is something external). So from this pov I surely consider better the Kasumi/Phase 4 cover compared to something that put Marie on the same plan of Kasumi (for the reasons overmentioned, not because I dislike the character).
Just so you know I complained about Marie being next to Kasumi on the site the second I saw it about a day after the official site went live. xD I thought I posted a status a while back and was looking for it but I guess it was in some random thread.
It's Japan and it's DOA! XD It does look like some idol/love sim game though... The background is also not that dark and there are sakura and rose petals falling, lol.