There is a risk when using devils that they will become unhappy. Deal massive damage to the conjurer then leave. DOn't let the devil re-engage you over and over as you flee. It becomes very happy and will be throwing maladicts like crazy.

If you can't beat the conjurer in a straight up, work on letting the devil slip back from happy to neutral...to pissed off.

I've had lesser ice devils jump on me when chasing someone (after not engaging for a while). Its annoying to have to go make your devil happy (mob killing) when prepped and ready for a fight.

It is viable to kill the devil or elemental if you are prepped and can withstand the rounds needed to pull it off. (FOr raid situations especially). The log with CHarine raiding is a perfect example. Kill the devil at the destructor. The conjurer then has to wait 50 hours or so to rebind. If you are losing, you now have time to heal off maladicts or go on the offensive. Go take the scepter while the conjurer is without servants and needing to wait 40 hours to bind. The scion will be that much weaker without despoil, nightwalker, ect.