As everyone has already pointed out Kruber doesn’t need as much prescision as Kerillian. That being said, I really don’t have problems getting headshots when it matters. If you followed @Positron’s build there are only a few mobs you really NEED headshots on: chaos knights, hookrats, storm sorcerers, and bosses.
With “On Target” slotted I have no problems doing this, it’s simply a matter of learning the attack animations and movement patterns of each. Any headshots you get besides those are free ammo and crit buffs.
I really can’t believe you’re complaining about getting 25% free crit chance. You don’t need to build items around this for it to work. Kruber’s native crit is around 10%, add a 5% crit trinket and get one headshot to be critting 40% of the time. This is incredibly good. It allows you to kill chaos knights in legend with a few headshots and no career skill; it allows you to punch through more enemies in the horde and get more ammo back; it allows you to body shot enemies you normally need headshots on.