It seems that the Right-Trigger is no longer mapped to anything in-game. Powering rooms on/off has been moved to Left on the D-Pad and Skill 1 is now Down on the D-Pad. Once you reach an elevator the Right-Trigger does absolutely nothing, impeding any further progress. I have tested this with a wired X1 Controller and connected wirelessly via the Xbox Wireless Adapter. My entire playtime with this game has been while using a controller, the controls have been properly mapped all year, not sure what has gone wrong.

Edit: Looks like Heal Hero is unmapped. Up on D-Pad seems to do nothing. Also, when you press Left on the D-Pad to Power Rooms On/Off even the Right-Trigger graphic across the top of the screen animates. I've tried Verifying game cache and booting the game -> disabling gamepad -> restart to take effect -> enabling gamepad controls -> restart to take effect -> starting  a playthrough to test controller mappings. I'm gonna try to re-install now.

Edit#2: Re-installing the game didn't help. Moving the game to another hard drive also didn't help. I also tried removing each DLC and update one by one and that also didn't help. I also noticed that the "Rest" command to refresh character skills in the pause is also unmapped.

GAME VER: 1.1.5
GAME PATH: F:\Steam\steamapps\common\Dungeon of the Endless
DX DIAG: https://www.dropbox.com/s/ocsr5u0m9utnq8f/DxDiag.txt?dl=0

OS: Windows 10 Pro Build 14393 (Anniversary Update Installed)

Link for the Steam thread: http://steamcommunity.com/app/249050/discussions/0/305510202672608076/

Forgot:

Version 1.1.5 with the Australium update and Amplitude Badge DLCs

--Edit-- 

Just downloaded the Death Gamble and Organic Matters, no differences, power room is still bound to Dpad <- instead of RT and RT doesn't do anything

@devs, check out this awesome video from the steam dev days 2016. It explains how to do controllers the right way:

https://www.youtube.com/watch?v=7I4SiAiKqqk

ATM I cannot play this game which I've boughed for me and 2 of my friends. We like to play couch coops, and having bought a game that doesn't work is sad. Please look into this bug.

@GothikaGeist, to complete your nice opening post:

- Dpad-up does do something, it is mapped to skill2

- You can use the elevator using Dpad-left, same as powering rooms

The real problem is not being able to heal the heros, the minor problem is that all the in-game labels indicate the wrong buttons.