I'm a somewhat experienced game designer, yet creating a 30-level character class for Dungeons & Dragons 4th Edition intimidates the hell out of me.
I don't want to just tweak an existing class, for licensing reasons. I may publish this.
Adam, I designed three new 4E clases for Goodman's Forgotten Heroes and helped develop and playtest nine of my co-authors'. Here's what worked for us:
Decide what the key appeal of the class will be. How will playing this class be different from other classes with the same role? (It helps to answer this for all the existing classes within that role: how are they different from one another?)
Work out the builds for the class. What are two different archetypes for the core concept? What mechanical choice will make them feel different in play & reinforce their theme?
Design the class features (including the build choices) and four at-wills. Make one PC of each build, choosing different at-wills for each. Why does this build like these at-wills? If you made a human PC and had three at-wills, is there still good choices or do you feel like some at-wills are less desirable? You want all four to be pretty appealing to both builds.
Playtest your builds as part of a party of core classes. None of them have anything but at-wills: you're just seeing if their essential mechanics work as intended.
Once that's solid, design the encounter powers (as these can be build-specific) for a seventh-level character of each build. Get it so that, at the heroic tier, these define the key cool that's specific to each build. Playtest with a party of core characters using only their build-specific encounters to benchmark. Then fill in the other one or two encounter powers at each level - the ones that either build might want.
Now design the heroic tier daily powers. These are not build specific, and can let the class do something outside its role (like a fighter doing a blast attack). You might also design the utility powers from 1 to 30 - these don't get replaced, so you can lay them all out now as a guide to what kinds of awesome the class will be capable of.
Once you've got the heroic tier solid, do the next two, one at a time. Think about which powers someone will replace as they level up. Is there a new power for them to choose that maintains the special schtick of their build and concept? I like to iterate powers - take one that worked at heroic and soup it up at each of the next tiers.
Balance powers as you write them. Does it have damage equal to other powers of a PC with this role at this level? Effects and increased accuracy will trade off with lower damage. You can't avoid having some powers be a spin on an existing one - just try to be sure the idea of the power is clearly expressed and fits the PC concept.
The best way to playtest higher level characters is to make PCs. As you go through the process of making a paragon or epic PC, are some powers obviously superior or worthless? Can you find exploits with feats, paragon multiclassing, or epic destines that 'break' your design?
The only way to playtest it is not only threw play, (not to say that you shouldn't use play, but no need to reinvent the horse everytime you want to take a buggy ride)
one can use all that playtesting already done by looking at the powers that are already out there mechanically and extrapolating from that. Its not perfect but it goes a long way to ensuring your not churning out 30 levels of crap.
If I was going to build a complete class for Dnd 4e, The first two big questions are:
What is it's role, and what is its primary stat.
Once you have a role, and a stat, decide on secondary stats (one for each build you plan on) and the builds they will power.
Once you have the builds thematically in mind, make some class features to help ensure that the class can do its job. This means strikers probably need a scaling extra damage feature, leaders need a heal 2x encounter, defenders need a mark and mark enforcement and controllers are left with whatever utility you want to give them.
With builds and roles in mind, choose the hps and surges you want from the example given by the iconic roles (wizzy, cleric, rogue, fighter).
Choose your starting weapon, armour proficiencies and impliment proficiencies (if any)
Choose your defence boost if any
Chose a class skill and a class skil list as well as the number of skills to select (from 3-5)
Choose a power source
Start building your powers, start with the at-wills (1 dice of damage + stat mod and a minor effect or just stat mod of damage and a major effect, minor being a shift or the like, a major being a full blown status effect)
Start out the rest of the powers.
Lets see if this works
Role: Controller
Power Source: Arcane
Primary Stat: Intelligence Secondary Stats: Wisdom (Nature Trapper) or Charisma (kind of a con artist with
Class Skill: Arcana
Class Skill List:(Choose 3):
Bluff, Diplomacy, Nature, Dungeoneering, History, Insight
Proficient: Simple weapons, up to Chain Armour,
Proficient: Trap Impliment
Build Options: Nature Trapper, City Slicker
Hps at first level: 10 + Constitution score Hps per level gained: 4 Healing Surges per day: 6+ Constituion modifer
Class Features: Mechanical Mastery: You gain proficieny with one exotic weapon Sudden Jerk: Anytime you move a creature with forced movement you may move them 1 addititonal square. Ambush: You gain a +2 bonus to deceptions that will result in phyisical harm to the opponent.
At-Wills
Bear Trap - Trapper attack 1 at-Will - Trap
Standard Action Area 1 square within 2 squares Target: First creature to enter the square Attack: Int vs Reflex
hit: 1d10+Int modifier Effect: The Creature is slowed until the end of your next turn. Nature Trapper: The Creature is slowed (Save ends)
Foot Trap - Trapper attack 1 at-Will - Trap
Standard Action Melee 1 Target: One medium or smaller creature Attack: Int vs Reflex
Hit: 1d6+Int modifier damage Effect: Creature is knocked prone City Slicker: You may move your charisma modifer squares.
Weapon Trap - Trapper attack 1 at-Will - Trap, Weapon
Standard Action Area 2 within 2 squares Target: Any creature that starts their turn in the area Attack: Int vs Ac
Hit: 1[W]+Int Modifier Damage Sustain: Minor Special: This trap requires a weapon when used. As long as this trap is in use or sustained, that weapon cannot be used for any other attacks.
Encounters
Rumble - Trapper attack 1 Encounter - Trap
Standard Action Melee 1 Target: One medium or smaller creature Attack: Int vs Reflex
Hit: 2d6+Int modifier damage and target is pushed 1 square City Slicker: you and your allies may shift 1 square. Nature Trapper: Target is knocked prone.
Rakes, Rakes everywhere - Trapper attack 1 Encounter - Trap
Standard Action Melee 1 Target: All enemies in the area Attack: Int vs Fortitude
Hit: 2d10+Int modifier damage Miss: Half Damage Effect: any creature hit by a rake must end their turn immediately.
Daily
Improvised Explosion - Trapper attack 1 Daily -
Standard Action area burst 2 within 10 Target: One Creature or Object Attack: Int vs Reflex
Hit: 3d10+Int modifier damage Nature Trapper: Objects take double damage. City Slicker: You may use this power and choose to have it do no damage. If a creature moves into the area of this power within Charisma Modifer Rounds, the trap immediate deals damage to them as a hit.
The powers are the real thing that needs balancing but as long as you avoid crazy stuff (infinite hits even if conditional, dozen's of W, the big bad condition (stunned) it should be pretty useable. (and yes I know my formating is a bit off, this is just a quick example, it should show the basics of a class is very easy to draw from trends)
Instead of a 30 level class, I would really focus on developing the 1-10 Heroic tier, and then give yourself a moment to try that out before tackling the Paragon and Epic levels. Otherwise I agree with what a lot of other people here are saying as for how to do the rest
Really, most classes do not have "unique" powers at more than a few levels;
Level 1 needs an at will attack; it's darned near universal.
there should be one or two truly iconic powers per bracket (1-10, 11-20, 21-30), but they can be anywhere in the powers structure.
Then fill in the rest by lifting the mechanics from equivalent level powers from similar concept classes; rewrite all the flavor text, make a couple small mechanical adjustments, and revise to unify the theme.
Then playtest it. Revise as needed.
Well, I don't have a step-by-step guide, which, I'm sure would be a god send, but, like most things in 4e, the easiest way to start is to take something that already exists and customize it.
There's a good amount of 4e content that is almost exactly the same just flavor-texted different. The hardest thing thus about designing a 4e class is making it feel significantly different from existing classes.
But, when designing a new class, look at the role you want it to play, and the theme you want it to have. The theme usually plays a large part in the 'power source' for the character. Then, when you have those two things picked out, look at the existing classes that are that type or have a power source similar to the one you want your class to have and begin customizing.
As far as playtesting all 30 levels, unfortunately, the only way to playtest it... is to play ;).
