Ergh... I'm really not fond of the 3x weakness to Fire here (Weavile, Tangrowth, and Magnezone). It wouldn't be quite as bad if you were this weak to something like Rock, but Fire's one of those really common attack types. When a couple of Flamethrowers can take out half your team, you have to question your strategy.
And now that I think of it, you're 3x weak to Ice as well! Togekiss, Tangrowth, and Donphan can all get wrecked by Ice Beams - another very common move for special sweepers. And there may be others, too. Since you really don't want to have any more than two Pokemon weak against any given type, you may have a lot of problems with this particular lineup...