Banette can be a insanely hard deck to play if you dont know what your doing.
As for Plox being able to beat Banette, I think that if they player using Banette is a novice Plox has a better chance.
Let's think about the following situations with Plox.
First, 3 Crystal Beach is the play. Any less and your asking for trouble. Some will most like play 4.
Okay, lets take Dusknoir - Most Plox are going to try to get up Gardevoir before they go for Dusknoir. If they go for Dusknoir first they are going to fall behind quickly. While Dusknoir does have the ability to be able to make it hard on Banette, the fact of the matter is that Banette is so quick, that a good player will have only 3 Benched Pokemon.
Gardy Lv. X - Okay so you are going to Bring Down them, and if they play more than 1 Shuppet your are going to use Dusknoir bring 1 of the 2 to your hand. So let me get this straight, your going to let my active Banette attack you turn after turn, while I knock out your Gardevoirs? Wow that makes tons of sense.
After that, I dont think I need to explain any further. Plus look at FL States Results. Everyone play Plox/GG and Banette went Undefeated and WON THE TOURNEY.
JMO,
Drew