I've given up hope of politically-appointed prosecutors ever doing a thorough and effective job of this. Sure there are some high-profile cases (AT&T, Standard Oil, Microsoft (almost), Google (maybe), etc) but the vast majority go unprosecuted.
There are really only two ways to fix the antitrust disaster:
1. Private right of action (like RICO) for the Sherman Act -- let nonprofits and individuals file the charges. This takes the implicit pardon power away from politically-appointed prosecutors.
2. Graduated corporate income tax, which creates a natural diseconomy of scale. The income tax code already contains a decades-old mechanism (search for "common control" in the IRC) to prevent evasion using shell-company shenanighans. It's very well tested, it works, and it has been working since the 1980s -- mainly to prevent US persons from evading the extra requirements for owning controlling interests in foreign corporations.