So, having tried this build out, it becomes very obvious that it's pretty sub-optimal. Rushing BT only really works on champions with enough base damage from abilities to do any damage. Getting ruanaan's after it, and then Phantom Dancer gives you lots of Attack Speed, but without any AD, your attacks will barely tickle anyone with more than 10 bonus armor. Twitch is the kind of champion who really needs on hit effects to do anything. I've had better games with support twitch that rushes BotRK, then Ruanaan's and Black Cleaver for shredding armor. He relies on BotRK to do any damage, and the slight bit of life steal helps in extended fights. I liked the build in theory, but in practice it was just lacking.