For Charizard, I think you should replace fire blast with a move like flamethrower or even heat wave. They both still do good damage, have better accuracy, and you can use them more.
Excadrill seems to be okay.
For Mamoswine, I think you'd be better off getting it the ability Thick Fat, but only if you can find one with that hidden ability.
I think Greninja seems pretty good.
Scizor seems to be pretty awesome.
For Alakazam, you can leave it the way it is. But, with it's magic guard, it'll already be taking damage from only attacks (that is unless you're concerned about the opponent healing itself). You can replace Taunt with Calm Mind, Reflect, Light Screen, or any other stat boosting move. Again, you don't necessarily have to, if you want to leave it the way it is, I think it'll be great either way.
Hope this helps and if you're confused about something, don't be afraid to ask! :)