Dice just discussed the upcoming update will bring changes to Irish. According to their data Irish is one of the least picked specialists in the game. So because of that they have decided to nerf him...
@AngrySquid270 Upon the Sentinel being placed, it'll have a warmup time of 1 sec. Once it stops its first projectile, it will become active and stop others only for 5 seconds, at which point it will go on a 7.5 second cooldown