Mostly applicable for first two bosses in Dunar Temple, but possible to work elsewhere if you could find the same situation.
You can stand in the water near both the shark boss, and the fire elemental that would normally reset them, and auto attack them (along with some moves like tornado for sorc) and the constant hitting them will make them not reset but unable to fight back.
Some moves like meteor for 2hand sorc will not hit them, but also won't reset them. Some moves may reset them, but all sorc auto attacks do not. Be careful when spamming auto attack to not leave the pond you are in or get too close to the edges or they will aggro you, fail to hit you because you're in the water and reset.
This is mostly useful on survival mode as the fire elemental constantly resets otherwise because his room is full of small puddles.
Not sure if this is possible for melee or archer, but works for sorc so it should work for archer as well.