It all depends what kind of team you're up against.. and who's fed, and if you're doing well or not.

If tanks(or health stackers) are the problem, grab a bloodrazor, the black cleaver(reduces armor). if low on cash, last whisper or yomuu's ghostblade.

A magic heavy team, get a defensive item like force of nature or banshee's veil. Then get Wit's end or more damage if youre confident.

You shouldn't have any trouble with melee dps, you can kite them to death afterall :D

If youre doing well you could get 2 bloodthirsters so you can stay in the fight longer.

Double up is nice skill, but I don't like it nether. Nice build. If you have extremely long game, how do you continue your core-build? bloodrazor and bloodthirster?