Status effects are where a lot of the potential nightmare lies in retrocloning 4e. They make up most of what makes attack powers unique, there are a hell of a lot of them (16 in total), there’s no clear ranking of what’s more powerful and by how much, and pretty much none of them are identical to the named effects in the 3rd edition SRD. This means that you have to come up with the wording yourself and avoid replicating what’s in the rulebooks.
It’s going to take a while to figure out how much each of these is worth. This is just the first pass, and it’s not taking into account things like duration or number of targets (these present modifiers of their own.) I’m not trying to be authoritative, just making some estimates.
Blinded: A blinded character can’t see (naturally), takes -10 to perception, grants combat advantage, and can’t flank. The earliest this shows up for characters is at level 1 for the Battlemind’s Twisted Eye power, and only when that power is Augmented by 2 power points (which is more or less equivalent to an Encounter power in terms of how often it can be used). Comparing that power to how most normal Encounter or Augment 2 powers increase in damage, a blinded effect seems worth around 1D. Potent, but can still be accessed early.
Dazed: A dazed character grants combat advantage, can’t flank, and on their turn has to choose between a standard, move, and minor action instead of all three. They can take free actions as normal, but no immediate or opportunity actions. This pops up a lot in early encounter and daily powers, and again seems worth around 1D of damage.
Deafened: Deafened characters can’t hear, and take -10 on Perception checks. This seems less powerful than blinding- again it shows up in Level 1 dailies to start, but usually alongside other elements (persistent zones and the like. The fact that it has no obvious “now you suck in combat” effect means it’s more of a perk.
Dominated: A dominated character is dazed, and their action each turn is determined by a dominating creature (though it can only use at-will abilities.) This is a biggie. The earliest it shows up for PCs is as a level 5 daily, for the Bard’s Song of Discord, and that power has two effects- the target is dominated, and makes a basic attack against another NPC of the Bard’s choice as a free action. A free attack against the enemy is worth quite a bit too, of course- a monster at that level might deal 13 damage, and a daily for a level 5 PC could be worth 20.5, but domination for a turn is effectively worth another free attack, plus negating the attack the creature would have made on its turn. This sort of thing seems hard to cost, but 2D may be on the low side.
Dying: A character at 0 or fewer hit points is unconscious and makes a death saving throw every round. This is not really a status that powers inflict beyond taking creatures to 0 HP (and NPCs/monsters at 0 HP or less are just out of the fight normally).
Helpless: Helpless characters grant combat advantage and can be targeted by a coup de grace. The first time this pops up as a status PCs can inflict is a Wizard Daily at level 9, and then only if the target fails a saving throw against the initial effect- and the Daily does no damage beyond inflicting these effects. Severe effects like this are best used very rarely to begin with- one of the nice things about 4e is a lack of “save or die” effects which end fights before they start- but I’d rank this as even more powerful than domination when it comes up at all. Maybe around 4D worth of damage.
Immobilized: An immobilized character can’t move out of their space, can teleport, and can be subject to forced movement. This first shows up in Encounter 1 powers, where it seems to count for about 1 die of damage.
Marked: A marked character takes -2 on any attack rolls not targeting the creature that marked it. This is of course key to how the Defender classes work, and for them is practically not worth putting in a power since they have ways of marking enemies to start with. (Though it’s easier for some than others.) For non-defendery classes, like the Bard, it’s a perk- not worth taking away damage dice but a good rider effect.
Petrified: Petrified characters have been turned to stone; they can’t take actions or perceive their surroundings. On the upside they don’t age and have a damage resistance of 20. The first time this becomes available is as a level 9 daily, again another one which does no damage.
Again this is another “use very sparingly” thing, but I’d say it’s worth 4-5 dice of damage.
Prone: A character who is prone grants combat to anyone making melee attacks against them, but has a +2 to defenses against ranged attacks so long as the attacking enemy is not adjacent. Prone characters take -2 to attack rolls, and you can use a minor action to drop prone. This is a common one, and works out more or less as worth 1D of damage.
Restrained: A character who is restrained grants combat advantage and takes -2 to attack rolls. They’re also Immobilized, but can’t be moved by forced movement. This first shows up in a Fighter 1 Daily, albeit one that requires good tactical positioning- still this seems to generally show up in the 1D range.
Slowed: A slowed character has a movement speed of 2 (unless it was lower to begin with.) This doesn’t apply to forced movement or teleportation. Shows up first in an at-will which does 1D + ability modifier damage, so it’s a basic “perk”.
Stunned: Stunned characters can’t take actions, can’t flank, and grant combat advantage. This looks to be worth around 3 dice of damage, and is another “use sparingly” one.
Surprised: Surprised characters can’t take actions or flank, and grant combat advantage. Since this happens at the start of combat, it’s not a thing that characters inflict via attack powers- it’s determined by circumstance.
Unconscious: Unconscious characters are helpless, take -5 to all defenses, can’t take actions, can’t flank, and must fall prone if possible. A Level 1 Wizard daily can inflict this but only after a failed save, and common sense dictates it should be more powerful and worth more than helplessness (which is bundled in) or stunning. Could possibly go as high as 5D, lower if the target wakes on taking damage or being attacked, etc.
Weakened: Weakened characters deal half damage with their attacks, not counting ongoing damage. This is a fairly common status to inflict and seems worth around 1D.
As you can see, we are a long way from making this an exact science. Powers can get very complicated in terms of the trade-offs and side benefits they have, not to mention secondary attacks, ongoing effects, etc.
And we can’t assume the designers always got it right. I’ll be mentioning a few unbalanced elements and how they might be rectified later on, and it’s possible any or all of these have been under or overvalued by the rules team.
For those wanting to make 4e a simpler game there’s an opening here- if you’re willing to accept more abstract status effects, you can narrow down the list- in particular I see “dazed”, “stunned”, “helpless”, and “unconscious” as being increasingly severe versions of a general impairment. This isn’t what I have planned for Untitled Space Opera Project but it may be helpful at higher levels.
All input on how powerful these effects can be in play is welcome.