Although the team seems rough, I definitely do think that your suggestions are better. But you'd be shocked how hard it is to kill Meganium when he is played well. He has single handedly won me a lot of games because of the DEF investment and Reflect combo. I use the Rotom-W in combo with the Meganium because they counter each others weaknesses.
The Mega Banette isn't totally a suicide Poke though. With his pretty good ATK stat, fully invested, I definitely like using the Destiny Bond as a final resort. It's usually for Pokemon that I can't kill like Ferrothorn or Venusaur. So it is definitely useful when it needs to be. Since he does get Prankster, he also can Will-o which makes a lot of physical sweepers useless with the Reflect combo. The team has a lot of synergy.
But the Meowstic I made just for fun, and I was trying to incorporate it into a team, but it's just really not good. I am trying to find something for a solid 6th. But yeh, I just usually use lower tiered guys and they could work if you really want them to. It's a little more fun to me that way.
The Mega Banette isn't totally a suicide Poke though. With his pretty good ATK stat, fully invested, I definitely like using the Destiny Bond as a final resort. It's usually for Pokemon that I can't kill like Ferrothorn or Venusaur. So it is definitely useful when it needs to be. Since he does get Prankster, he also can Will-o which makes a lot of physical sweepers useless with the Reflect combo. The team has a lot of synergy.
But the Meowstic I made just for fun, and I was trying to incorporate it into a team, but it's just really not good. I am trying to find something for a solid 6th. But yeh, I just usually use lower tiered guys and they could work if you really want them to. It's a little more fun to me that way.