No it wasn't. At no time was Vanguard/Powertech the best overall class. It was an easy class to play that you didn't have to be a good player to contribute. It was good in the fact it was the only class that was great against guard swaps since it double dotted (extra 25% damage overall) when someone has guard up on your target.
I have only been playing since January but before 2.0 I think pyro powertech was one of the top 3 specs in the game. Now it is probally closer to being in the bottom 3 worst specs in the game.