Hmmm... interesting point. I was obviously using the card draw to aid the ability, but it might actually hinder game progress. I catch that most of the time, but not here. I could change it to requiring an exact discard. That way, you're encouraged to play cards out.
that'd reduce the problem, but I can still construct a board where this could be blazingly fast. just to demonstrate, I'll use perfect shuffle luck, but it's not necessary.
t1,2: open ironworks(Ir)/chapel(Ch) (doable with either a 4/3 or a 5/2)
t3: CCCCIr, Ir for Investor (In), buy Village (Vi) (7/14)
t4: CEEECh, Ch everything (2/10)
t5: ViInIrCC, Vi to draw C, In to draw CC, Ir for In, buy Vi (2/12) (and you can gain an incidental VP here by holding back two coppers)
t6: CCChViIr, Vi to draw In, In to draw CC, Ir to gain Vi, Ch to trash CCCC (4/9)
now my 9-card deck is 1 chapel, 1 Ironworks, 2 investors, 3 Villages, and two copper. it's now pretty easy to chain everything together, use my ironworks to keep picking up investors and villages, and end every turn discarding a chapel and a copper, playing the other copper to get it out of my hand. and once I run out those two piles there's really no incentive for me to shut off my engine and empty a third pile. I might do it if there's a cantrip available to works for, like wishing well or spy, but otherwise I can just sit back and let myself get as many VP as I got investors, and, if I want, I can skip a turn of points to Chapel those coppers away and just use my chapel and dead works to trigger it.
now, that is with perfect shuffle luck and the best trasher in the game. but even if it takes a couple extra turns to set up, you still wind up in a pretty strong position pretty quickly. I find it hard to believe that, with those cards, you couldn't have your deck down to pretty much just villages and investors in by turn 10, giving you plenty of turns to get up on points. it's not going to happen on most boards (the relative slowness of most other available trashers gets in the way) but it can become a very strong, degenerate game state that amounts to a rush for investors if the stars align. and, since the speed at which you chapel and the location of your ironworks in the shuffle make such a huge difference in how well you do, it's often going to come down to luck. and if I have a 6-investor stack and you have a 4-investor stack, there's really not much you can do to come back besides hope I get stuck on a 5-investor hand a couple turns in a row.
note that a deck that picks up all 8 provinces winds up with 51 points. that's equivalent to 10 turns of getting 5 investors. so if you can get that set up by turn 10, you can expect to beat a province rush if the game goes to turn 20 or so. Smithy Big Money, if it ignores other victory cards, clears the province stack around turn 24. also, with the ironworks you can pick up more investors if he doesn't contest them, leaving you with even more points. and if he does contest them he's bogging his deck down with moats for the occasional incidental VP, which makes things even faster. in total, I think this probably suffers from Fancy Balance Issues, to use WW's term. it's gonna be a moat with some incidental VP in 90% of games it's in, but when the stars align just right and it falls on the board with chapel (maybe steward or ambassador), ironworks (or workshop but it's not as good), and a village variant, you're going to have a stupid-good engine that has no actual need to end the game, and the game will be decided almost exclusively by the investor split.
