Well, to start with, I play the game on PC with a controller....I have always found the keyboard to be awkward to use to play the game...I much prefer the finer control a controller gives you. I use a PS4 controller simply because I like the feel better than an x-box controller and the touch-pad allows me 2 extra buttons. There are however 2 really big drawbacks to the controller:
1. This one isn't big and easy enough for me to tweak settings to fix myself...but please take off the 1st/3rd person view mode from your controller default. Until I re-mapped that button, I cant tell you how many times in PvP I accidently went into 1st person mode and died because of it...in controller mode this should retain its default keyboard mapping only...this also frees up a button that can be used for something more useful...anything more useful.
2. This is the big one: Camera sensitivity...IT IS TERRIBLE, set all the way to max AND using a 3rd-party program to increase sensitivity it is STILL stupidly slow to turn the camera....this makes melee PvP absolutely miserable....a templar running around you spamming jabs for example is almost certain death since YOU JUST CANT TURN FAST ENOUGH. I mean, I accept this gimping as the cost of playing PvP with a controller, but I have had to learn to play around it in creative ways and am handicapped because of it...please, please, please increase the sensitivity. Try this test ZOS...using a keyboard streak through a group of enemies and turn around to attack them again...a flick of the mouse and you are facing them again, using a controller though you have to start turning as soon as you hit the streak button...its a major handicap that needs to be addressed, as if the limited number of buttons wasnt bad enough.
3. Honorable mention: When zooming out on the Cyrodiil map(or any other, but mostly annoying in Cyro) Holding the LT button, it takes FOREVER to zoom out...with the mouse, a quick spin of the scroll wheel will get you there. Luckily this doesn't affect actual gameplay...but it is highly annoying and needs to be fixed as well.