Miller having a good start to the season doesn't change the fact that the trade was, and still is a bad one. It had and still has a chance to massively backfire should the lottery go poorly, and even if that doesn't happen Tampa is still going to get a good pick.
At best, Miller has turned the team into a mediocre team instead of a bad one. Which isn't a great situation, mediocre is the worst thing a team can be. Never good enough to win anything, never bad enough to get the superstars needed to become a great team.
The Miller trade is a classic short term 'save my job' move. The best thing long term for this team was keeping that draft pick, and the low salary/years of service that ensues along with the chance of getting a superstar.