If Winged Horde is broken what do you consider the Invoker's at wills? Busted to all hell? Winged Horde is very much in line with Divine Bolts or Grasping Shards, weaker in fact. I'd gladly trade the "only enemy" of Winged Horde for the slow effect on Grasping Shards. Grasping Shards is complete own on melee creatures who are at range.
What the heck are you talking about?
Grasping Shards: Target: Each creature in burst
Winged Horde: Target: Each enemy in burst
Advantage: Winged Horde (major advantage)
Grasping Shards: Attack: Wisdom vs. Fortitude
Winged Horde: Attack: Intelligence vs. Will
Advantage: Winged Horde (+2 to hit statistically)
Grasping Shards: Hit: Wisdom modifier radiant damage
Winged Horde: Hit: 1d6 + Intelligence modifier psychic damage
Advantage: Winged Horde (3.5 extra damage except against undead, so the majority of the time)
Grasping Shards: the target is slowed until the end of your next turn
Winged Horde: the target cannot take opportunity actions until the end of your next turn
Advantage: Neither. This is totally situational, but Slow is rarely helpful except when a foe is trying to run away.
Winged Horde totally owns Grasping Shards.
Sure, if the Invoker (typically low Dex) happens to get a quick initiative and the melee foes happen to be more than 4 away from the front ranks and they have no ranged attacks, he could once in a blue moon prevent them from closing in round one.
Big deal.
I'll take a more damaging area effect attack that can be used every single round against multiple foes over that occasional use any day. Grasping Shards is balanced with Scorching Burst because it has a minor control, but it goes against the worst NAD and does less damage.
As for Divine Bolts, it's behind the Winged Horde curve as well, but much closer:
Divine Bolts: Target: One or two creatures
Winged Horde: Target: Each enemy in burst
Advantage: Neither (the advantage of Divine Bolts to attack up to 2 foes within 10 is offset by the number of times that Winged Horde can attack 2, 3 or more foes in a close burst 1, especially within melee conditions)
Divine Bolts: Attack: Wisdom vs. Reflex
Winged Horde: Attack: Intelligence vs. Will
Advantage: Winged Horde (slight advantage, just over +0.5 to hit statistically or 5% more dpr per foe)
Divine Bolts: Hit: 1d6 + Wisdom modifier lightning damage
Winged Horde: Hit: 1d6 + Intelligence modifier psychic damage
Advantage: Neither (psychic resistance/immunity occurs less often than lightning resistance/immunity at least in the MM, but it's hard to measure all products, especially for feats and synergies)
Divine Bolts: nothing
Winged Horde: the target cannot take opportunity actions until the end of your next turn
Advantage: Winged Horde (Divine Bolts has no control, whereas Winged Horde can allow the Wizard or other PCs to move past a foe or foes protected)
No doubt about it. Divine Bolts is overly potent (borderline broken if not broken for a controller power). It's nearly as powerful as Twin Strike for a non-Striker and has control as well. But Winged Horde is still better and still broken.