I won't even go into this new sub-phase concept.
It's not new -- it's the rules. "Action" as ready is concerned isn't the same thing as the use of a power -- a power will typically involve multiple discrete actions, performed in order, and a readied action (or any other Immediate Reaction) can take place between them.
Next, you have two possible outcomes: trigger was tied to movement or trigger was tied to non-movement.
There's no real difference here, except that each square of movement is a separate trigger (ignoring "if an enemy moves more than two spaces" or such)
Resolving the trigger being tied to non-movement action is simple. Your action happens after the triggering action. Completely counter intuitive but that is it. I am not sure why you would not simply delay and then be able to select your power on the fly...
Aside from the "because you get to act before their minor/move actions" issue, because the rules here aren't what you think they are.
There are, in fact, very few reasons to ready an action in response to an attack (usually, you're better off just acting or reading in response to movement), but immediate reaction powers that respond to an attack work well as advertised--the Avenger 2nd level teleport can get you out of harms' way before an elite's second attack hits you or before the dogthing that just knocked you prone gets to maul you. OTOH, readies in response to preparation (of any sort) can be very effective; movement is an obvious case here, but in a tense situation, "hit him if he draws a weapon" can be quite useful, and there's no way that the foe can draw a weapon and -not- pull the ready (even with a power that draws the weapon and then attacks, those are two separate actions as far as the Interrupt rules are concerned).
Resolving the Trigger being tied to movement is not as simple, your action happens after a move of 1 square because each square counts as a potential trigger for an immediate reaction. So when setting your movement trigger you have to define which square or squares you want to trigger your readied action.
True. But you can specify a really broad net here. You don't have to specify specific squares; you can say "adjacent to an ally", or "moves closer to any of us", or anythign that actually covers your intentions.
Another key point of confusion is if they use a movement power then you turn your readied action into an interrupt and are able to attack them before they activate their power.
If one actually understands how interrupts work, this isn't nearly as difficult. There's no real difference between using a Readied action to push someone away during a charge before they make an attack (though if they have enough movement, they can just keep going) and using an Immediate Reaction to move away between an elite's shield bash and their main attack; in both cases you're moving after the action you're responding to, but still during the power you're responding to. All Immediate actions can happen during powers; the difference is merely whether the explicit thing you're responding to happens, and then the immediate action goes off, or whether your immediate action rolls back the thing and does its own thing, then the immediate action happens and might not work as well as originally intended (or at all). There's a big difference between "II: gain +4 to AC when you're hit by an attack (thus, you're no longer hit by an attack)" and "IR: gain +4 to AC when you're hit by an attack (you're still hit by the attack, but might avoid the followup attacks, if any)."
So things like: coming around the corner, moving within range, moving adjacent or shifting are acceptable triggers but these are not: moving away from you when you have a melee weapon, jumping behind complete cover, dropping prone, doing jumping jacks.
Moving away from you when you have a melee weapon works fine if it's a reach weapon -- you get your opportunity attack (which does move at Interrupt speed) and then you can make an attack with them one square away from you. They do something, you do something.
Dropping prone works great; they drop prone, then you hit them.
Jumping behind complete cover can be worded right (jumps toward cover; tries to take cover) and if so you'll get them in midair before the jump completes, but they do get one free square of movement before you get to go.
Not really sure what's wrong with jumping jacks here. They do jumping jacks, then after the first one you hit them.
The movement to attack before the attacker attacks is very crude game design and seems like a very arcane way to get attacks to go off before attacks.
Only if you don't take it as a specific point in a more general case -- that actions in the Immediate system are fairly small things (individual lines in a power), not big things (entire uses of a power). As such, they clarify that individual squares of movement are triggers, rather than the movement entirely (thus a polearm fighter can get a good wack at an enemy who goes through their area of control, if they specify a reasonable ready, whereas if the entirety of movement were one action they couldn't).
Conceptually what the readied action is for is to make an attack before the enemy attacks- at least that is what it is used for in many games. But not in 4e.
I think this is really a 3eism. I know of no other game with detailed readied actions, and I think the habit of saying "I ready an action to attack him before he attacks" comes from 3e. Plus if you just want to attack before they attack, you attack on your own turn.
In 3e, you had some wierd and wonky cases where you're ready actions specifically because interrupting the enemy was more powerful than not --enough to be worth messing with your initiative and mabye losing your action. You could disarm in response to an attack (or knock prone); inflict massive damage to make a spell fizzle, etc. That's all gone -- you do that stuff with powers now, so readied actions instead serve a powerful but more limited toolkit.
In 4e, I think what a readied action is usually for is for doing something reasonable when you -can't- attack. An Immobilized melee specialist could throw something -- or they could ready an action to hit anything in range. A ranged specialist could approach an enemy running flyby attacks and try to flush them out (and probably get surrounded and ganked) or they could ready an action to attack the enemy once they enter view. A wizard, low on hitpoints and not willing to take the fight to the enemy, can ready an action to thunderwave any enemy that gets within two squares of her, sacrificing her attack for a more defensible position (and so on).
So there are still some unresolved issues:
Can you select more than one trigger? I heard one opinion on it so far and I would like to hear more. Some of the funkyness could be cleaned up by allowing multiple trigger actions, "If they attack or move into these defined squares I use my power."
I think this is a GM judgement, really. IMO, readied actions should be accepted if they are a comphehensible single thought (I'd be cool with "if they attack or move", personally) and rejected if they're more complicated than that (and, of course, you have to specify the action your'e using in response, so there's only limited flexibility there).
I would like to hear some opinions on what should the play at the table be like? How should the DM approach announcing readied actions and how should the players announce them?
What are some good alternatives to this system? Simultaneous actions, interrupt actions, simply use delay, what else?
In general, you need to specify what you're doing when you ready an action -- it can be pretty open ended ("if he makes a threatening move"), but it needs to be clear enough to rule on. Players need to specify exactly what their readied action is (except for PVP, where they need to tell the GM exactly what their readied action is); but a character only knows that the opponent (if visible) is readied for somethng, not what they're waiting for. (The GM needs to know the details of readied actions to act as a referee, but monsters are -not- the GM; nor are players).
I'm not about to suggest house rules here, but I do think there are situations where Immediate powers are much more powerful than readied actions (that's why they're powers, after all); there are also plenty of cases where one is better off using delay than a readied action (but not all of them, by any means). If you know what you want to do and when (but can't do it yet), you might want a readied action. If you want to respond to anything, but don't have something very specific in mind, just Delay.
