[Urendi Maleldil]

Actually, I think it's better to keep mine sweepers separate. That way if you don't have enough sweepers to completely clear a mine field, you will only loose the sweepers and not your entire battle fleet.

It's also useful to have a single disposable scout ship enter a potentially mined sector (like a warp point near an enemy sector) before sending your main fleet in. It's also a good way to get rid of obsolete designs that are too much trouble to retrofit.