I'm no expert when it comes to marketing, but will offer my 2 cents anyways
When it comes to words that get people interested, I think 'zombie' is a big one these days.
I know the grays aren't your typical zombie, but In terms of a description I think it would work well.
Something like 'zombie action puzzler'
The word survival also seems to grab attention due to the meteoric rise of games like Day Z, and while
SH isn't technically a survival game, in any world where the undead are taking over, survival is going to
be implied I guess. You are technically survivors.
I agree that the term roguelike or roguelikeish is misleading, maybe you could get away with 'roguelike inspired'
or something, but i'm not sure.
When it comes to the features list, I think the 'grays aren't your typical zombies' section could be worked into
the description of the game rather than a feature.
Also maybe put something in there about the fact that you can replay the levels for higher scores and gold
completion through certain objectives, people love a bit of competition and challenge
I agree with Mick when it comes to the rewording of the 'follow the story of Darrell and Mary' section.
In terms of something like a steam page, I think a good bold tagline at the top, then a section about how
the grays are more than your typical zombie and a little about the world/how the game plays, then a list
of features would be great.
I will put on my thinking cap and see if I can come up with anything more substantial