So lat's start with the basics: How many standard, by the book Orcs are a balanced fight for a party of four 1st level PCs?
But since we never see a balanced party...
A few or probably several years ago, probably shortly after 3.5 came out, a DM on these boards called the CR/EL system "poorly constructed" (I think they used a single, short word, actually) due to an encounter he'd just put his PCs through. His PCs were used to 2nd Edition, not 3rd, and in
my opinion didn't know the rules of 3rd Edition very well.
Ogres were CR 3 in 3.0 and CR 2 in 3.5. The DM wanted to use the original value.
The 1st-level party was not optimal to start, IMO. They had a wizard, and a druid, a ranger (instead of a fighter), and a rogue. The wizard opened combat with a magic missile. Now, I understand that spell was the bees knees in 2nd Edition, but this was a different ruleset. Also, throwing a magical bolt barely larger than a dagger at a 9 foot tall muscular humanoid seems a bad idea to me even if you know nothing about the rules.
The party got flattened. Therefore ogres were clearly OP.
The battle could have gone quite differently if the wizard had started with Color Spray or Sleep instead. The ogre would fall asleep or get stunned by the flash of light, the rogue would repeatedly sneak attack it, the fighter would hit the stunned ogre and the druid could sit in on a log and snooze. The PCs would have lost one spell and taken no damage. The
exact same PCs facing
the exact same ogre.
Player level plays too big a role.
In fact, facing orcs? What type of orcs? Are they all generic 1st-level orcs? Are they all identical? Did any of them take a slightly different route and throw javelins instead? Are they all 1st-level barbarians? Just one of them, maybe their chief? If they're all generic 1st-level warriors, they all have the same strengths (namely, strength) and the same weaknesses (low Int, low Reflex and Will saves). This probably gives the PCs a huge advantage, such as when the wizard says "I cast sleep!"
How do we adjust if the party is only three? If the party has six characters?
It makes too much difference who is missing or who has been added. IMO low-level clerics are weak. You'll hardly notice if a cleric was missing from the battle, but you'll certainly notice afterward!
Now, what do we do when they make a level? Abandon Orcs forever? How many do we add to match that extra level?
I know that these are baby steps, but I think we need an agreed upon foundation before we build anything bigger. And while these questions are already covered in the rules, we know that those rules break down after a very few levels. We're trying to build something a bit more solid.
The math isn't perfect at any level, not even first. At 1st, you're swingy. You have few hit points, but can probably kill an orc in one shot. (A 5th-level fighter facing a 5th-level orc barbarian probably can't kill it in one shot, but probably won't be killed in one shot even if it's a crit.)
Now let's talk prep. In a Pathfinder campaign I'm in (I know, it's not officially 3.x, but it's very close), we went through three encounters that struck me as interesting. Two were linked together. In the first two, we got to prep ahead of time. Many PCs were buffers and self-buffed. The wizard cast Blur and Mirror Image, then womped on the single boss monster with Hideous Laughter. Said boss didn't get up for four or five rounds, by which time we were mopping up.
We immediately rushed into the next encounter before our buffs ran out. However the EL was much higher, and while again there was a single boss, let's just say barbarian rage (which gives bonuses to Will) and Indomitable Will saved its day. It basically killed our barbarian in one round, despite his incredible AC and alchemist buffing. Prep gave us a big advantage, but not enough to guarantee a win.
On another game day, we were "ambushed" by half-dragon werecreatures. We didn't fail our Perception checks, but it was an "ambush" in that we were
not prepped. (To be fair, the enemies weren't spellcasters, so they couldn't really prep either.) We also have some odd weakness against AoE attacks such as breath weapons. However, we'd gained a level, and my druid PC summoned an elemental which immediately vacuumed up half the opposition and deposited them in the midst of clashing armies.
So, which encounter is "standard"? Usually high-level parties have some idea of what they're facing, to the point of scrying or otherwise collecting information before diving into combat. (And the enemy can do the same.) Is it reasonable to expect non-prep on either side at such high levels? Sure, that happened in that encounter I just mentioned, but the enemy had bred those creatures away from their main camp, so our scrying didn't catch them.
