You are wrong. Page 59 of Player's Handbook states "A conjuration uses your ability scores and defenses to determine the outcome of attacks it makes and attacks against it (if such attacks are possible)."
Show me where in that line of text it states that 'it doesn't make any attacks, you do'.
PHB3, page 216. Right side of the page.
Attacking with a Conjuration: Normally. a conjuration cannot attack.
If your conjuration can attack, you make the attack. You determine line of sight normally. but you determine line of effect from the conjuration. as if you were in its space.
Conjurations that make attacks are, by the keyword's definition, you making the attack.
Fireballs are not Conjurations.
The Player's Handbook clearly contradicts you.
The PHB does not say you are not making attacks through conjurations. You're mistaking 'Something not mentioned as true or false' as a contradiction, which is actually not a contradiction, but merely the absense of evidence for or against.
However, the conjuration keyword's been cleaned up and explained in the two or so years since then, and it's the most recent definitions that we go by.
The power does not need to attack to provide its combat advantage no more than a flanker has to have attacked the flankee in order to, well flank. It just has to be there, harassing enough that it provides that bonus.
Lastly, Incindex---
Could you explain the possible benefit of granting combat advantage outside of combat? While I understand (and the DMG suggests agreement with) your rhetoric in general, it's not really appropriate to this particular power.