M10 is a joke, since it is only useful as a throw away tank to trade for a super heavy in a risky dive.
That's not true. The M10 is very good at it's role, which is to counter medium tanks. You rush one or two out, counter axis' mediums and unleash the damage with the howitzer Sherman. Also the M10 is a beast at crush damage and is an unorthodox way to deal with blobs. Combined with the dozer sherman you have a lot of wipe potential.