It's harder to debt dive in the sense that you're now forced to defend yourself if you want to do that. Under the old system, you would need all 9 available shares to be bought, then for one AI to pay double price for the last share, which just wouldn't happen in time.
Now, because of the AI's tendency to attack players with low stock prices, if you debt dive and don't defend yourself, you're vulnerable to several AIs buying into you and getting the majority buy. For this daily, for example, I let the AIs get 5 shares in me (at which point there are several of them at 100% on me) before I'm forced to sell out of my short early to buy one AI up to defend myself. Defending myself would be trivial, given that two stocks would be cheap to buy, but in pushing the limits for a good time, you generally don't want to spend money on anything but making money. So while I happily tried to win every relevant auction on debt-diving dailies under the old system, I'll mostly avoid auctions now.