I regard this as a waste of turns personally, because during this you're inflicting absolutely zero control. Sure you're doing a piddly amount of damage that will eventually kill it, but you're also not doing anything to hinder that enemy doing whatever it wants to do. If that is kill the rogue in those 4 rounds, nobody is going to think you're doing a good job as a controller. On the other hand, the Wizard smashing 3 creatures with Beguiling strands, bunching them up and then dropping a scorching burst or other AoE power on them has done something far more useful with those 4 turns.
What is the most important type of control? The answer is death. If a foe is dead, then he cannot attack back (as a general rule shy of some monsters bringing NPC allies back from the grave). So, damage is the ultimate form of control.
You'll note that I said multiple times that area powers are flat out better when the Wizard can manage them. And I also said that at low level, the Wizard runs out of Encounter powers quickly and is quickly limited to At Will Attack powers.
With regard to single target At Will Attack powers, let's look at the control that you are talking about:
Cloud of Daggers, Erupting Flare, Nightmare Eruption. 95% damage, 5% control. These are almost never used as a control spells. They are all about damage.
Illusory Ambush. Almost all damage. A -2 penalty to attack rolls is ok, but unless it forces the DM to use a single target attack instead of a multiple target attack, or to use a weaker attack, it has little to do with control. It has to do with protection. And for single target NPC attacks, the -2 penalty only works 6% of the time (60% chance to hit * 10% chance to have the NPC miss when he normally would have hit).
Ray of Frost. The first of the hard control powers. It is good for preventing a foe from escaping, but in the scenario that you were discussing (i.e. the first attack on a foe), it rarely helps as control. An NPC that is slowed can still shift and attack, or charge up to 4 squares and attack, or use a ranged attack. The control aspect of Ray of Frost (and the chance to hit) is fairly limited.
Storm Pillar. Also a control power that uses damage to control, but it's use too is extremely limited. When the situation calls for it, it's nice. No doubt. But, the situation rarely calls for it. It's easy to just walk out of it shy of a narrow area (with the exception of the center square if it is placed 5 feet about the ground directly above a foe). As a general rule, it's tough to set up a situation where the NPCs will give up their attacks in order to not move through it and they can often just sidestep it. And if they have ranged attacks or some types of burst or blast attack, the spell does virtually nothing unless the PCs can also create forced movement.
Charm of Misplaced Wrath. This is a good control spell at times. However, not every Wizard will have it. Every Mage has Magic Missile. Slide and daze with zero damage is nice under the circumstances that the foe cannot just charge back into battle. For example, slide a melee only NPC either 2 or 7 squares away from every PC and he cannot melee attack at all. But, if the NPC has a ranged attack or some forms of burst or blast attack, it's pretty limited. Sure, the NPC cannot get Opportunity Attacks (a minor form of control), but this spell totally gives up damage in order to set up a select few types of melee NPCs. More often than not, Magic Missile is better.
There is no doubt about it. Area effect powers are typically better when the Wizard can use them, and as a general rule, he should when he can. If not though, the other single target attack spells typically result in less average damage than Magic Missile and very little extra control.
At higher level, Magic Missile loses its luster due to the plethora of extra Encounter and Daily Attack powers and the damage boosts to the other Single Target At Will powers. But at low level when a PC typically only has one or two Encounter Attack powers and has a greater need to save his only Daily attack power, Magic Missile is a solid choice over most of the other single target At Will Attack powers (build depending).
