Magic Missile was errata'ed to that form before essentials was released.
And this is putting aside the fact that almost everyone else in thre group thinks Essentials is a further dumbing down of the system.
Streamlining is a more accurate word. I like the new Essentials builds because it means that I can spend some of my time in combat watching what the other players are doing and enjoying the "story" aspects of it rather than flipping through papers thinking "Was that power an Immediate Interrupt or a Free Action?"
It's also nice to know that when the opportunity to use an Immediate action arises, I will be paying attention and jump in to use it, instead of having to tell the DM 30 seconds later "Oh yeah, I can stop that whole thing from happening", which pisses him off and grinds everything to a halt.
I've only seen this level of not being able to pay attention start to occur at low to mid Paragon where the number of individual player options (i.e. powers) starts climbing significantly.
The theory that Essentials streamlines the system is mostly (but not completely) dependent on which Essentials class one plays and which powers one picks..
Normally, I'm not interested in simplifying and streamlining, but I think pre-Essentials 4e reached the point where any combat ran the very high risk of at least one of the following problems:
1. Players neglecting some of their options and opportunities because of difficulty tracking
2. Serious grind because of slow decision making
3. DM and player frustration (and sometimes hostility) because of excessive bumbling and out of sequence interruptions ("oops, I meant to...")
Now maybe the problem is that I've gotten too old and my brain doesn't work as well as it used to... I'm sorry, what was I saying? Oh, right... but I welcome the simplifications, limited though they may be.
Do you know how MANY feats and magic items a Wizard PC has to have (and one has to have items and feats that are perfectly designed for this, i.e. no toughness or unarmored agility because the PC is focusing on damage) to get to 18 or 20 average damage at low level?
Once in a blue moon? Like I said, my low level play experience disagrees with your armchair assessment.
But if I can drop the opposition from 5 foes on round one to 4 foes on round one? You bet. Drop him, decrease enemy damage by 20% right away, and change the action economy from 5 on 5 to 5 on 4. That will save healing surges and other resources every time.
But an enemy being exactly at or below 7 or 8 hp is a pretty small range, even at low levels. I'm not sure I'm sold on the suggestion that you have an enemy precisely at that point in one in every three rounds. You've claimed that is your experience, and that's fair enough; I'm nonetheless not ready to call that typical.
Armchair aside, I've certainly played and run in tons of games - even without Magic Missile being present, it is usually noticeable when an enemy hovers in single digit hp, and it certainly hasn't been as common in my games as it has been in yours.
I think there will be times when that is the case, sure. But there will be plenty of other times when an enemy is at 11 hp, and another At-Will would be the better option.
But there is also the hypothetical scenario where your MM then leaves him with a few hp left, and was also a wasted action.
And, honestly? I'd rarely expect to see a wizard breaking out MM on round 1 - if you've got one injured enemy and several other foes, now is probably when you should be breaking out your multi-target powers.
My claim isn't that Magic Missile is bad, remember. My disagreement was with your claim that MM is so good that a wizard who isn't using it 1 out of every 3 rounds is playing badly. And I really haven't seen any examples thus far to back up that claim.
Again, Magic Missile is especially useful in the right scenarios. Just... not the ones you've really mentioned. For less optimized characters, it is on par with most other At-Wills. It is a useful tool to have on hand in the right situations.
But something that every good wizard should be casting 1/3 of the time? Not even remotely.
My suggestion is this:Okay, I've asked some of my players and quite a few are against including Essentials in the game, saying it is a dumbing down. This is how I feel about it, but it's beside the point.
I'm beginning to think it's a bad idea bringing in Essentials if so many are opposed to it, the guy still wants to play a mage but I am starting to worry.
Final decision won't be until after he has played it, which won't be for a few weeks.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.