Some of the results are pretty hot but the chances of anything game breaking is akin to pissing into a cup on the ground from the back of a 747 flying at 30,000 feet.
I have tried for some low level gear for my BLM for a while now to no avail. Mostly focused on feet since there aren't many decent choices there... was just trying to get 1 or more INT on an feet piece. Never came out with anything better for my BLM just lots of elemental shit and a few with like +1 STR or +1 DEX +1 acc.
Most recently tried to add an INT to a cunning earring. Ended up getting +5 HP -5 MP +1 acc on 29 earring. Its obviously not an upgrade for my BLM but going to hang on to it for low level melee.
I don't know why SE thought negative augments was a good idea, but I can imagine why they'd have gone for random augments in general. Crafters have complained for years that durable good crafting is a dead end, because most people already have the items. They never wear out, so there's a cap on demand for them.
But now we have augments. The items people have get used up (finally) in the augment attempt, and the result is rare/ex. The item is now out of circulation, and if the augment wasn't a useful one, the person will need to get a new one for another attempt. That makes a larger market for crafted items, which we've needed for a while. Also, I think it's a better idea than the "charged item" attempt, which really didn't add much to crafting.
Eh not bad. Still doesn't really add anything to it. If that was str dex att or acc it would be sweet but agi and int? meh. Better then -str or -dex though.