I try to take it on a per encounter basis. One vampire may be more interested in self preservation, and avoid the cleric. Another may be driven by rage towards the gods and seek to kill the divine characters first.
Usually as intelligent foes gain levels I have them recognize/anticipate all the lower level tricks, but still not expect the PCs newest abilties and tricks (until hit by them at least once).
Real villians tend to know the PCs very well, and act on this intimate knowledge. In addition, foes under the direction of the villian have specific goals and strategies to deal with the PCs as they were when last spotted. Knowing the PCs newest strategy is to constantly push foes into a harmful zone effect may result in a group of dwarven skirmishers that blitz the caster.
Usually as intelligent foes gain levels I have them recognize/anticipate all the lower level tricks, but still not expect the PCs newest abilties and tricks (until hit by them at least once).
Real villians tend to know the PCs very well, and act on this intimate knowledge. In addition, foes under the direction of the villian have specific goals and strategies to deal with the PCs as they were when last spotted. Knowing the PCs newest strategy is to constantly push foes into a harmful zone effect may result in a group of dwarven skirmishers that blitz the caster.