League of Legends (LoL) Question: Fiddlesticks Top

So I've seen this build emerging where you'd run Aftershock on Fiddlesticks, play him top, and build him as a tank. It's actually been working decently great for me. For those who don't know, you'd go Frozen Heart, boots (defensive), Spirit Visage, Zhonya's Hourglass and an additional two tank items (like Randuin's Omen against crit etc.)

I was wondering if this build was really viable- it's not been like I'm winning all the matches and I lose sometimes in lane especially against AP threats. Is this build troll or does it have potential/worth building? And then comes my next question, against AP threats like teemo, would you get Spirit Visage first? Rushing Frozen Heart has been GREAT in the few Ranked Games I've played because of how much defense and sustain it provides. You can just perma-W and heal back from any negative trade.