they only waste 50% of your ink, which is very generous compared to other sub weapons. unless you're using a weapon that consumes a lot of ink on it's own, which to my knowledge there aren't any with disruptor, than you should have plenty of ink left to splat an opponent. if you really are having trouble managing your ink, than you should try using some ink savers (which are really good now because of the recent patch) or ink recovery up (which got an even better buff). otherwise you should work on managing your ink. Don't be constantly spreading ink because than when you're facing an opponent, you'll be out of ink before them especially if you're gonna use disruptor. the safest way to use disruptor (or any sub weapon) is to recover most of your ink (at least 75%) and than throw one. don't throw one when you're tank is half empty.They do no damage, no ink and you then need ink to try and splat the opposition.