The Staff I agree is a fantastic implement, perhaps even with the Orb depending on what you value.
But let's compare the Orb to the Wand as they are both offensive implements.
The Wand can increase your chance to hit an enemy with one of your powers from 40-50% to something like 75-95%. This is very good. it can practically assure you slap that nice status effect on them when it really counts, so that they wont be able to act for a round, or your enemies will have a better chance of hitting them for a round, or maybe you're just making sure one of your heavy hitting daily or encounter powers doesn't miss.
The Orb increases your chance of downright killing an elite with a single spell from 45% (with spell focus) to about 75 or 80% in the paragon tier. That's really, really, REALLY good.
Why is that? Because applying it to the first save against Sleep means they're very, very likely to fail it, and when they fail it, they're Unconscious, and when they're Unconscious, your entire party can coup de grace them with encounter and daily powers, and then spend action points to coup de grace them AGAIN with encounter and daily powers.
In short, the Orb is so awesome because Sleep is so awesome, and Sleep is so awesome because it takes a difficult fight and makes you automatically win it if they fail their first save because not even solo enemies can survive two rounds of coup de grace attacks.
Against a party of 5, a solo is 100% of the opposition, kill it and you win. An elite is 20% of the opposition, kill it and you pretty much win too because it's your 100% vs their 80% from pretty much round 1.
When I read Sleep+Orb, this is what I see:
Sleep Wizard Attack 1
You exert your will against your foes, seeking to overwhelm them
with a tide of magical weariness.
Daily * Arcane, Implement, Sleep
Standard Action Area burst 2 within 20 squares
Target: One really important creature in burst
Attack: Intelligence vs. Will
Hit: The target has an 80% chance of taking quadruple damage from all of your allies attacks, losing all of its actions, taking a -7 to all defenses, and dying if it takes damage from a single attack equal to it's bloodied modifier until then end of its next turn.
Miss: The target is slowed (save ends).