Well, first off, the Dwarf Rings did not (that we know of) make their wearer invisible. In fact, the only ring of the Great Rings mentioned to have that ability was Sauron's own, and even that only turned wearers of a lesser degree of power invisible; its power increased as the power of the wearer increased.
Secondly, the Dwarven Rings still did evil in that they kindled a great lust and desire for gold and treasures, even more so than the normal dwarf. This could mean, given the already easily-wrathful nature of the dwarves, that they would go to great lengths and commit great evils to get a treasure of their desire (think of the battle over the Nauglamir except intensified by the Dwarf rings!... scary).
The Dwarf Rings were, in my opinion, the most mysterious of all, but certainly their bad outweighed the good.
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...where the instrument of intelligence is added to brute power and evil will, mankind is powerless in its own defence.
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