The phrase "at best erratic" is correct and usable in written English.
It can be used to describe something that is inconsistent or unreliable, suggesting that the best possible outcome is still flawed.
Example: "The project's progress has been at best erratic, making it difficult to meet the deadlines."
Alternatives: "at most unpredictable" or "at best inconsistent".
But funding is at best erratic, and Oliver's hopes to have a ministry in every city have not materialised.
Deprived for so long of their captain, Michael Vaughan, and finest bowler, Simon Jones, England's Test performances were at best erratic while their one-day form had the burnish and purpose of a hastily assembled pub side.
As the countries of the former Soviet Union and Eastern Europe have made the transition from state control of all aspects of economic life, the evolution of health care markets has been at best erratic, and the need for a better managed transition has become apparent.
Unfortunately, some baseball players are going to continue to use PEDs and MLB's enforcement policies will, at best, be erratic and incomplete.
In what looms, at best, as an erratic third-place finish after 13 consecutive years in the postseason, the Yankees used the brand to hype this "last season" and the "last game" in the House That Ruth Built and That the Steinbrenners Will Soon Be Leveling.
In many parts of Latin America, postal service outside of major business centers is erratic at best.
Consumer spending is erratic at best, and bankruptcies are rising to record levels.
It's hard to fly when you don't have wings, and her writer's income is erratic at best.
Burnett, who was erratic at best during the season, pitched five and two-third innings, giving up one run on a solo home run by Victor Martinez.
I adore mint, not least because it seems almost impossible to kill in planted form, which is handy as my enthusiasm for balcony horticulture is erratic at best.
