Would this fit in at all,I dont know all the story etc and probably am a bit ignorant but I thought there might be twists where at some point you ally up with Diablo to overcome a greater threat,you know maybe you have to ressurect him then being the Lord of lies he tricks you at the end and you still have to defeat him or deprive him of gaining power to be even stronger than before.And yes I know its very cliche
You know I can imagine Cain saying 'You know what you must do,God help us all'.
The tricks is in the game now. It is up to us to choose our actions. Diablo can control our minds...but it can be hard for some of us to see it. Each time a player kills a player - it helps Diablo. At least in hardcore every pk is an Diablo ally. I am not sure if I help Diablo or not if I kill a pk.
That sounds like something they should do once they've exhausted EVERY other option as far as plot goes. It's like how when they ran out of different crimes on the original CSI, they had to start putting in bits about the investigator's private lives... BOOOORING. Turned it from a science-style crime show to a soap opera.
That's sorta what this idea reminds me of... something out of "Passions" (a joke of a tv show that you should be happy you don't know about).