Level: the level of the character or monster.
Monster Init: average initiative of a monster of that level. I must confess that I grabbed these numbers by simply looking at the initiatives of a lot of post-MM3 monsters in the compendium, so there could be sampling issues. Also, while lower level monsters have a plus or minus two variation, higher level monsters have a lot more range in their variation. Despite all this, these numbers are in line with the ones that I've seen here.
Primary Init: this is the initiative bonus of a character whose primary ability score yields an initiative bonus. For example, a Thief or a Deva with Battle Intuition and Wisdom as his or her principal ability score. This assumes that the ability starts at 18, is raised at every opportunity, and that the epic destiny also raises it by two. No other bonuses (such as feat or item bonuses) have been added into this score.
Delta: the difference between the two colums to the left.
Delta for L+2: the difference between the initiative of a monster of level +2 and the Primary Init score of the same level. I added this info because it seems that this is often a normal encounter.
Normal Init: this is the initiative bonus of a character who, at creation, has a 12 in the ability that yields an initiative bonus. There is considerable variation here, and while it could be a point or two higher, it could also be a point or two lower. This only increased at levels 11 and 21, and therfore the bonus increases at level 21.
Delta: the difference between Monster Init and Normal Init.
Delta for L+2: the difference between Monster Init two levels above the Normal Init.
Feat+Item: the bonus to initiative granted by taking Improved Initiative (+4 feat bonus) at level 4, retraining it to Superior Initiative (+8 feat bonus) at level 22, and donning a tier-appropriate Casque of Tactics (+1/2/3 item bonus) at levels 6, 16, and 26.
The conclusion I draw from the numbers above is that a character who does not invest in his or her initiative will, at higher levels, almost always lose initiative. While I can agree that such a character should be penalized to some extent, a ten or twelve point difference, on average, is too much. And forcing a character to invest a feat or a head-slot item to remedy this seems, to me, coercive. In other words, if I don't have an ability score that contributes to the initiative as a primary attribute, I am forced to spend a feat and a head slot item to remain competitive.
This is not as big a problem as the attack vs defense disparity. But it's a real enough issue to players who want to build mechanically-sound characters. For example, almost every character optimizer takes the feats and has an item bonus to initiative or has some gambit to optimize initiative.
The solution is to allow characters to add their highest bonus to initiative instead of dex, and apply a penalty to it if it is not dex. This should allow it to scale properly throughout a character's career. What do folks think about this?