I like to save crackshot on a treasure that has more than one guardian so it's quicker to kill them and your explorer takes less damage. But for some, like the lone outlaw rider, I crackshot because just fighting it (if there is a lack of towers) seems to take forever and you lose more explorer hp.
Some, like the lone carib blowgunner, I used to crackshot, until I realized that if you switch to melee, they fall pretty easily.
ESO: Steel_Reign
*Doles out the harshness*