I don't mind the low damage they do but it having a time limit is totally unneeded, this change would allow for a more thoughtful approach when using this skill allowing players to set up a spot in a map with many traps and then luring the enemy into it :D
It would be much fun than the way it is now were you just throw it on the ground in mid fight :P
Another suggestion would be to change the mastery itself to allow the traps to stay longer in the map.