Considering that you will almost never get the full build out, what you get as the last item is debatable. It's more circumstantial than anything. BT's just a suggestion. Doran's ring early on gives you enough AP to get early kills. This isn't a build designed to sit back and play it safe. You have to get kills immediately.

why blood thirster i mean hex tech gun blade shuld give you enough life steal
could it be like and inf edge or sumthin and dorans ring it would be a better as a dorans sheild for the health regan to stay in a lane.