This "stealth" game have one of the best first person combat systems, many cool fatal abilities, good combat animations. Why they bothered with it to much? It's just a waste of resources if player can't play that way.
Dishonored was probably meant to be played stealth but they didn't really advertise it as stealth. I remember the trailers looking decidedly unstealthy and showcasing in your face combat and supernatural powers, not so much skulking in the shadows.
Yes, marketing and gameplay are two very different things. There are strategy games that are marketed to look action-packed, for gods sake. It's laughable.
Buuuttt... That's no excuse for ignorance, IMO. It is ultimately up to the player to know what sort of game they are buying, and in today's day and age, there is zero excuse to not be informed beforehand -- there are user and critic reviews and tons of information available at your fingertips.
Though it is still a valid criticism of the games industry as a whole (But not something you can reasonably apply to Dishonored in particular), and it's something I wish wasn't necessary to sell copies. I wish games could be advertised only on their merits, and not have to resort to misleading or outright false marketing campaigns.
Hopefully they have non-lethal weapons and gear to help facilitate this. Maybe a stun baton or toxin or gas to knock out an enemy