I didn't feel quite at home without the controller support in the tactical mode, so i've been working on a JoyToKey solution for this. It's not perfect and you really can't use it for the avenger
and the menus but it works for me in tactical mode. I found out that
most buttons of the controller are already mapped out like in X-Com EU
but support of the analog sticks was missing. The already established
button bindings are nice but i had to work around them because they
can't be disabled and overriden so there are some quirks in there.

What you can do with it:

Control tactical mode (quiet good).

What you can't do with it:

Control menus and avenger mode (at least not reasonably good).

What already was there:

LT: Zooms out when held down
RT: Goes into aim mode like X-Com EU
rb: Switches to next soldier / next target (aim mode)
lb: Switches to previous soldier / previous target (aim mode)
Pad up: level up
Pad down: level down
Pad left: camera rotation left (When in aim mode you can scroll through the abilities but it will also turn the camera)
Pad right: camera rotation right (When in aim mode you can scroll through the abilities but it will also turn the camera)
Back: End turn
Start: Pause / Game menu
Y: Overwatch
B: Cancel (Exit menu or aim mode)
A: Accept (Shoot, Use choosen ability), Move soldier to courser
X: ? ... It should be reload but if you push it the gun just blinks and nothing happens ... ?

What I did:

Left Stick: WASD binding (Still digital controls and not
as smooth as in X-Com EU. I recommend reducing scrolling speed down to
3.)
Right Stick: Acts as mouse courser.
RT: Left mouse button - !!! You'll need that when choosing a hacking-option. Pressing A will only accept whatever is choosen.
X: When in aim mode you can use it to scroll through abilities
unidirectional. When you hold it for half a second or longer and then
release it your soldier will reload his weapon.

What you need to do:

1. Download JoyToKey http://joytokey.en.uptodown.com/
2. Install JoyToKey
3. Download X-Com 2 contols (Attached)
4. Start JoyToKey and load the X-Com2.cfg that you downloaded (I recommend to put it into the JoyToKey folder first)
5. Start X-Com 2 and try it out (Maybe don't try it in Ironman mode if you're not familiar with it yet)

What you can do:

1. Give feedback.
2. Improve it.
3. Come up with a better solution.
3. Enjoy the game.
4. Hope that Firaxis will implement proper controller support.

Thank you and I hope you'll like it.