There is no fundamental guide on "numbers of powers" as that doesn't exist on this level of abstraction. However, there are ways to quantify most of what a controller/leader does and apply it to the concept of party-as-character for purposes of optimization.
Let us start with the most difficult to classify, controllers. (And some theory)
While the other classes have axes the paper by myself and Russell: Damage Dealing (strikers), Damage Capacity (defenders), and Damage Mitigation (leaders), controllers have no epistemological representation as an axis because they do so many different things.
First, let us set aside the measurements of controllers that are adequately represented by other axes:
Damage Dealing can and does effectively eat their AoEs. It is possible to apply a multi-target multiplier as presented by me here. The math presented in that chart was derived from a Monte Carlo simulation that I believe has significant validity. Therefore, it is possible to build a "blaster" controller with reference to the striker damage chart. The trick is that the controller, by virtue of her multi-targeting, attacks the encounter as a whole. While this oft-times does more damage, the controller qua blaster is much less effective than a striker in "damage mitigation" by virtue of not applying that all-important status effect: dead.
Debuffs are quite adequately represented in damage mitigation or damage dealing.
If a controller applies penalties to a monster's defenses (causes it to grant CA, or equivalent thereof), that can be captured as damage dealing: you multiply the bonus in accuracy by the damage output of the other members of the party who would normally take advantage of your buff. If you apply increased damage, you multiply the normal accuracy of others attacks by only the increased damage (multiplied by your accuracy, of course).
Debuffs to the monster's accuracy or damage output are under damage mitigation.
The most common: dazed, is a pain to model. Most of the time, you're not going to be mitigating all that much damage from dazed. (Limiting tactical options yes, damage no.) Given that monsters can charge or do ranged attacks. You are, however, allowed to count it as mitigation if it accompanies forced movement, proning, or another character using the dazed to have the monster do less damage.
Still, debuffs are nominally damage mitigation.
Buffs should be treated as reversed debuffs (who'da thunk?). Benefits to PC accuracy are multiplied as above, And benefits to PC defenses are as above.
Sliding and forced movement is a right pain. As an off-the-cuff rule of thumb, slides of 1-2 should effectively be considered combat advantage, and 3+ for an extra target in another player's AoEs. Beyond this, I don't have any adequate models of the specific impact that a slide has as the slide resides almost purely in the mechanical-functional level of tactical expression on the battlefield.
With the edge cases out of the way, we can now look at the Damage Capacity and Damage Mitigation axes. Consider sections 2.2.2 and 2.2.3 of my paper.
Damage Capacity notes:
"A functional categorization of this axis articulates four benchmarks:
4 rounds, 8 rounds, 12 rounds, and 16 rounds. The nature of the system
makes it difficult to make a character able to survive less than four
rounds of combat (on average), and exceedingly few combats last more
than 12 rounds, much less 16. The higher numbers on this axis
represent a willingness to engage multiple enemies at the same time,
rather than a willingness to literally stand in front of an enemy and
ignore them for 16 combat rounds."
Thus, you can measure how your powers, through damage mitigation, impact other players' damage capacity. Defenders have it easy, of course. I would recommend a defender be a 12 round character and most others shoot for 8.
Damage Mitigation, as ever, is the annoying part, as it is a measure of how you influence other peoples damage capacity and damage dealing axes. As a theoretical axis its fine, but it is indeed difficult to quantify.
The best way to quantify it (not expressed in my paper due to length limitations) is if everyone in your party is using this model. Then you can measure the amount of change your powers create in the other two axes.
No change, obviously, would be the zero-point of the axis. And a lazy-lord would be the maximum, as they take no standard actions for themselves, but always use their powers to influence the other players' characters.
Functionally, however, there are no recommended "quantities" of actual buffs as they do not exist on the same mechanical-theoretical level as these axes. The buffs and debuffs are how one expresses these axes on the mechanical-functional level. Therefore, favourite no specific buffs when considering them on the mechanical-theoretical, but instead consider how they impact the party's damage capacity and damage dealing.
It is therefore possible to consider controllers and leaders in the damage-capacity and damage dealing axes if one considers the party as a single organism. If you calculate the everyone's damage-dealing capabilities, you should be able to observe the difference between that and the expected number of monsters who die to the party's hand per round. If there's a difference and you're a controller/leader, inspect your powers to see if they can make up the slack through the measurement techniques above.
You can perform a similar operation on damage capacity.