I've just started writing and building a narrative campaign based off of miniwargaming's Deffwatch rules but with a considerable amount of changes and homegrown guff. I've completed the base ruleset, as well as two full missions, the first of which has been playtested and makes for a nice introduction to this style of game. The storyline is vaguely similar to Warhammer 40K Inquisitor Martyr with a fair amount cut out and changed.
The basis is that 1 player is the dungeon master and has all the material available to them to run a campaign. While they control the "enemy" models on the board, the enemy models follow an AI set of rules, so the dungeon master isn't actively trying out special tactics and trying to purposefully kill the player. This makes it feel more like a dungeon crawler along the lines of Diablo II.
The other 1-6 players control six individual and fully customisable Deathwatch (actual) models, one of which is an Ork Painboy following Mad Dok Grotsnik's stats and rules. They go through the missions trying to complete all objectives and bonuses, gain XP, search for items, and get to put tonnes of upgrades on their individual guys. It's D&D meets Warhammer 40K 8th edition and thus far it's actually been quite for the players I've DM'd for.
I'll link all the resources below:
That link contains 1 rule PDF, Mission 1 and Mission 2 PDFs, and a sample 6 man roster on Excel that can be printed off for when people play and write upgrades as they happen.
I will slowly update that with more missions, and rebalance things if they become a problem over time or if something isn't working great.