In my opinion, it is a huge exaggeration to say that dwarves are useless.
At least, you can use them as doorstops, throwing projectiles or tripping hazards, so they are very useful and important creatures.
If you put a great helm on his head to which you have attached a candle by wax and wear a well-stocked money pouch on your belt, a dwarf can be a reliable mobile light-source, which are best deployed in dark dungeons and deep caverns. In place of the money pouch you can use a bottle filled with dwarven ale as well.