"If every encounter gives a perfectly balanced challenge, the game can get stale. Once in a while, characters need an encounter that doesn't significantly tax their resources, or an encounter that makes them seriously scared for their character's survival--or even makes them flee" (104).
Let me repeat that even to the creators of 4th Edition D&D think that perfectly balanced encounters make the game stale. Now, take that with a grain of salt though. When they say "perfectly balanced challenge", they mean balanced to absolute perfection. But the Dungeon Master's Guide then goes on:
"Easy encounters are two or three levels below the party, and might include monsters as many as four levels lower than the party: these encounters allow the character's to feel powerful. If you build an encounter using monsters that were a serious threat six or seven levels ago, you'll remind them of how much they're grow in power and capabilities since the last time they fought those monsters. You might want to include an easy encounter about one per character level--don't overdo it" (104).
I like the idea and intent of easy encounters; The designers got this spot on, but with the length of 4th edition combat, they just aren't worth it. I don't want to play out the same encounter that I know the party will eventually overcome without casualties for 30+ minutes. It's just not my cup of tea. Should an easy encounter only take 10 to 15 minutes to complete, I would consider them to be a great chance of pace and depth to the campaign.
"Hard encounters are two or three levels above the party, and can include monsters that are five to seven levels above the party. These encounters really test the character's resources and may force them to take an extended rest at the end. They are bring a greater feeling of accomplishment, though, so make make sure to include about one such encounter per character level" (104).
In my year of playing 4th Edition, I can tell you all that an encounter that is two or three levels above the party isn't really very challenging. It's a little tougher, but in reality, it just takes longer to complete. I did loose a character, Sir Rodrick the Warlord of Tallina, though to a encounter only two levels higher than the party.
"Monsters that are more than either levels higher than the characters can pretty easily kill a character and have a chance of taking out the whole party. Use overpowering encounters with great care. Players should enter the encounter with a clear sense of danger" (104).
You heard it: "Use overpowering encounters." That's right, the 4th edition Dungeon Master's Guide says to use them. Make your players run an cower in fear that their precious characters will die. Even most old schoolers believe that players should be warned when they are getting into a possible TPK situation. Take a took at these posts form Planet Algol: A Picture of a Dungeon Room With Cthulhu in it..., Another Rhetorical DMing Question, and An Explanation Regarding Recent Posts & TPK!
Taking the information above, here are some basic guidelines to creating varied encounters in D&D 4th Edition.
Roll a d10 to determine the encounter difficulty:
1: Party level - 1d4
2: Party level - 1
3-5: Party level
6: Party level + 1
7: Party level + 1d4
8: Party level + 1d6
9: Party level + 1d8
10: Party level + 1d20
This all being said, I'm not a huge fan of 4th edition D&D. But if we are going to discuss something with any real level of integrity, we need to understand both sides of the issue. In this post I have taken the time to analyze and discuss combat encounter balance of 4th Edition D&D and have shown that the popular mentality is incorrect and uninformed. We all, including myself, need to do better to insure that we use logic and understanding rather than pure emotional reactions when discussing sensitive topics and differences between different aspects of this magnificent hobby.