There are some totally OP class combinations ( most of them make no sense RP wise ) while it is very easy to make a totally useless char.
And that's a good thing. Fuck balance. I want some classes to be more powerful then other classes. I want some classes to be weaker. This is a natural result of having more options and it's a good thing.
That's what levels are for. If you want YOUR fighter to be a wand caddy, that's great, simply don't level him up. Sadly we only got one edition that treated martial characters with any degree of respect.