Hmm, Grasp of the Grave and Stinking Cloud are no less powerful than Visions of Averice when you take everything into account:
GotG has a 5x5 area which is easily increased to 7x7 with enlarge spell (VoA cannot be enlarged). Like VoA it targets enemies only. It automatically does 1d10+int necrotic damage and dazes the target, plus does 5 necrotic damage and continues to keep the target dazed so long as he is in the area or when he enters the area (VoA does no direct damage and immobilises targets which is more effective against melee targets but less effective against ranged targets). GotG lasts for an entire enoucnter without sustaining (VoA requires a minor action to sustain and another minor to repeat the attack against enemies which save, leaving the wizard with one standard action per round - effectively dazed himself).
Stinking Cloud has a 5x5 area which is easily increased to 7x7 with enlarge spell (VoA canot be enlarged). It does 1d10+int poison damage on a hit and continues to do 1d10+Int poison damage to any creature starting within or entering the zone (VoA does no direct damage). Although it does not hinder movement, SC blocks line of sight, rendering many ranged attackers within or beyond the cloud ineffective. It requires a minor action to sustain but does damage automatically thereafter (VoA minor to sustain). SC can be moved up to 6 squares as a move action (VoA cannot move and takes a second minor action, effectively a move action, to repeat the pull attack).
Both spells inflict damage directly, take fewer actions to sustain and can easily have a wide area of effect. GotG takes no effort to sustain and dazes targets automatically (VoA requires a hit roll to pull and immobilise), and SC can be moved if an enemy flees the area and does more damage than GotG or VoA. Which of the three spells is most effective at any given moment depends significantly on the circumstances of the encounter, but certainly not on one spell being inherently more potent than the others.
Both of them have a burst radius consistent with other daily powers across multiple classes. What I also like about these two powers is that keeping enemies (even dazed ones) in the zone requires more strategy, coordination, and effort from the party. While both of these powers may initially catch any number of foes within their zones, determined creatures can escape within a round or two. If the party wants to get them back into the zone they will have to find another way to do so.
Reducing the range of the burst will make the spell significantly less effective. Remember that the outer region of the burst only applies a pull efect on a hit, as anyone caught at burst 5 range, when pulled 3 squares, will be outside the burst 1 immobilise zone. What you are looking at is an effective burst 4 for pulling and immobilising, which is no better than a readily available burst 3 on the other two powers (with one very useful feat) for sustainable damage and other features. And even if your wizard can't enlarge the other spells, is a 2 square increase in radius not a fair exchange for a lack of damage and increased effort required to sustain the power?
