-Try not to throw everything you've got at a time(one single huge combat).Split encounters so that they aren't that difficult but continuous and fairly demanding,steadily exhausting your characters' resources.
-Throw different situations that require different cleric spells.(if all the cleric has to do is to kill giants,then he will load with Righteous might and divine power and will outshine others.But if he has to prepare a bunch of restoration ar a spell resistance then his chance to use the combo everytime in each combat will be significantly reduced.
-And about the BBEG,try not to throw a single very strong opponent.Reduce his power a bit and support him with a force of weaker ones.If all of your pcs attack the same opponent,no matter how strong he is,his chances to survive more than a few rounds are few.
A week ago i had a party of 4 players (level 7) attack an orc fighter(level 7) and a wizard (level 5) .In a straight combat this was going to be very easy for the party.However i had them fight a few encounters before they face the BBEG and there where 12 ogres in front of him when they finally found him.Even though the players got to play first they couldn't charge the orc fighter from the first round(and thus easily killing him).The evil wizard cast something to damage the party and the orc fighter damaged one of the players a lot without exposing himself so much(remember there are ogres everywhere around him).The combat was fun and i didn't use difficult opponents for my players.
It is always in your hand to control your players,and if nothing works,a good talk can do miracles.
I think it worths trying before you use the errata.Nobody likes to see his favored spells-powers beeing reduced like that.(you can use it anyway if nothing works)
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The Wizard