Powers are the most widely-recognized feature of 4th Edition; the At-Will, Encounter, Daily, Utility structure (AEDU) is both criticized for its “homogenization” of classes (though they each use the structure to do different things) and praised for giving a clear structure to balance their abilities. One Level 3 Encounter Power is, in theory, as good as any other.
Powers are also the biggest challenge for anyone trying to do a clone of 4th edition. Their sheer quantity is overwhelming, and going along with it, the game never really told us how to create our own. (Had the line lasted until a DMG 3, perhaps this would have happened. Perhaps.) It’s something that appears to never have been an exact science- there’s no fixed formula weighing different aspects- but we can both find patterns in the process and hopefully refine it.
Attack powers (Utilities are their own ball of wax) generally work on the formula of an attack which does up to multiple dice worth of damage, plus some perk related to the class it’s for and their overall combat focus. For attacks using a weapon, the die is set as [W]; nonweapon attacks name a d6, d8, etc. Damage is almost always increased by the class’s primary ability modifier (so most Fighter attacks do x[W]+Str, Wizard spells add the Int modifier, etc.)
If we call the variable die type D, we can then express most powers’ damage expressions as xD+Stat, and look at the typical spread by tier. At-Will powers do 1D+Stat to start out, and raise this damage to 2D + Stat at 21st level (the start of the Epic tier.) This isn’t much of an increase given the rise in monster HP over 21 levels, but this reflects that PCs will have more Encounter and Daily powers to use and more knock-on effects adding to the number of attacks they can make and the damage that they do.
At Heroic tier, Encounter powers typically do 2D+Stat, and Dailies 3D+Stat. This is less an average than a high end total, though. There are many powers which do less than this, however, and that’s because either the “perks” have gotten bigger- dazing an opponent is usually worth a die or two, for example- or they attack multiple targets. Within a tier, damage doesn’t usually increase but the “perks” generally get a little better.
At Paragon tier, the numbers improve to 3D+Stat for Encounter powers and 4D+Stat for Dailies. At Epic tier, Encounter powers hover more around 4D+Stat, and Dailies at 6D+Stat- with usually one power at level 29 that does 7D damage for when you really need to roll some buckets of dice.
But of course, the real math for how much damage the player characters should be doing is over on Page 42. In theory this means we can look at the “expected” average damage at a certain level, figure the average damage for a power (for [W] powers we can use the die type of the weapon the class will most commonly use, or the most powerful), subtract the latter from the former, and the remainder is how much all those status effects and forced movements are worth. In theory.
The first and most obvious question is what numbers to use. Obviously Encounter and Daily powers are limited damage expressions. Possibly Encounter powers would use the Medium Limited column, Low for burst and blast attacks; Dailies would start High Limited and maybe use Medium Limited for attacks which target multiple enemies. It’s a start.
And here’s where I admit I have not actually tried any of this. The powers I have created for my own project started are more my attempt to twist, mutate, and some times merely adjust powers in 4th Edition, though for legality’s sake I’ll want to replace whichever ones are too close to existing ones. My experience (which is still incomplete) is that it becomes easier as you go along and start to grok the zen of 4th edition, so like all forms of writing it’s a matter of practice.
But even as I work from an inexact approach of playing around with the kinds of effects that published attack powers have, I think there’s some potential in the idea of actually figuring out just how much a slide effect, or letting a PC spend a healing surge, or making an enemy grant combat advantage, is worth; this would make homebrewing easier not just for designers, but for DMs and players in 4e games. There is much to be done.