As I mainly play AD casters/bruisers (Darius, Jayce, etc.) I have been struggling with the new items. Since the release I have been rushing the new Black Cleaver as it builds from items I get first anyways such as Brutalizer and Health Crystal, but I have been finding that I no longer get Bloodthirster as usually the other slots are taken up. Mostly with Triforce,GA,boots, Randuins, and the new Scimitar. What are your opinions? Should I still find a mandatory slot for Bloodthirster?

On Darius? you really shouldn't be building brutalizer or black cleaver. Darius has his own armor penetration by leveling his E and really needs sustain so you should be rushing with him the phage and other health items because his damage scales well enough on it's own. If you feel the need to build a thirster on him it should be one of his last items.

On Jayce i think that black cleaver is his new staple. Instead of rushing a thirster you can build a cleaver and then go for trinity force. If you like to get the early scaling damage then you can get the thirster before the trinity force especially since the thirster went down in price and triforce went up, so it's more of a choice of whether you lots of damage or if you want a more rounded Jayce.

Another that will definately use black cleaver is Talon. He always builds brutalizer and black cleaver is just going to improve him but you'll definately get the thirster early on.

Gotcha, I do not build Brutalizer or Black Cleaver on Darius (for those reasons you stated) I was just including him to give an idea of people I play top, but Jayce I have been playing religiously. So would you say I should get the BT on Jayce but its merely a question of getting TF first or BT?