I can only say that I've tried an abandoned this a couple times in the past due to triple black casting cost. The closest I can remember it ever getting to what I would call good was in mid-range Bob-Tendrils decks back during the Dark Confidant days, but with the continued rise of big casting cost "free" spells like Fow, Gush (now more unrestricted than ever), and new additions like Dig and Cruise, Bob seems to have been sent back down to pitch in Triple A (also known as Legacy) for the time being. At least so far as control decks are concerned... (Black Fish decks with Bob and Deathrite and Necro...? maybe?)
I've long felt Necro was most useful in mid-range control decks (going all the way back to the black pump-knight/drain life decks) but it seems now it only sees play in storm decks. Does anyone have any experience with this? Perhaps with Monastery Mentor?
Necropotence was used historically almost exclusively used in two different strategic approaches: Aggro and Combo.
From 1995 until roughly 1999, Necropotence was used predominantly in Aggro decks. Then, in the late 90s, it was used in Pebbles combo, and then, most powerfully, in Trix.
In either Aggro or Combo decks, Necropotence was used to refuel and refill, allowing it to overwhelm the control pilot. Necropotence is the greatest card drawer of all time.
That said, blue- centered, multi-color control strategies have almost never used Necropotence to great effect.
The main problem with Necropotence in Control decks is this: Control decks often need multiple turns to set up and execute their finishers. Necropotence does not give you the time to do that. Necropotence really incentivizes you to win the game within 2 turns of resolving it - otherwise your life will be in a very precarious situation.
The secondary problem is casting it. Generating BBB in a control strategy is not easy, and Dark Ritual is usually paired with Necorpotence.
That said, there are decks that have used Necropotence that verge on control. In the mid-1990s, one of the lesser, but still played, Necro decks was mono black control, with a heavy discard suite, but with Corrupts and Drain life effects to buy more time and turns.
Similarly, I have seen Necropotence used to great effect in Lotus Cobra control decks.
Lotus Cobra allows a control pilot to accelerate Necropotence out quickly and generate the BBB without relying on card disadvantageous accelerants like Dark Ritual.