If you're worried about balancing how often the shards get found then consider using a card-based system or gap-based system rather than a straight 10%.
Card method:
There is a deck of ten drop cards, one of which is the item card, and each time a monster dies a card is drawn randomly. If a blank is drawn, no item. If an item is drawn, a shard drops. To stop predictability the deck is refreshed after an item is drawn, and a new card is always added if the deck gets down to 1 with no item found. This ensures a player is unlikely to go very long without getting any upgrade, and also doesn't get them too often.
Gap method:
Every time an item drops roll a 1d10 - that's the number of further kills required for the next shard. You can add more special cases to the 10 roll to again ensure it isn't too predictable.
Since these systems are hidden from the players it looks like plain random, but it ensures more balanced play.
Regarding the negative statuses, I'd say they can add flavour, especially if it's interesting like in kraflab's suggestion. Best way to find out is to test