Daze is incredibly strong. Very, very, very few things are immune to it, and aside from making your Reflex save (or maybe1 having improved evasion), there is no protection to be had against it. And force damage, of course, is extremely reliable. SR: Yes is a downside, but SR still isn’t terribly common at 7th level.
By comparison, black tentacles does vastly less damage, doesn’t have the advantage of force damage, and grappling both offers much better options for avoiding it and is in any case a far lesser detriment than daze is. SR: No is nice, certainly, but against things without SR (or whose SR you can reliably beat), wings of flurry is vastly superior.
That said, perhaps black tentacles isn’t the best 4th-level spell to compare wings of flurry against. For my money, solid fog is the quintessential “ok now that’s just not fair” 4th-level spell, because most classes offer absolutely nothing for getting out of it at 7th level. Solid fog is SR: No, has a similar area that can be positioned at considerable range (to wings of flurry’s zero), and lasts vastly longer than wings of flurry. It also imposes some conditions that are near-impossible to be immune to—the weather domain’s granted ability specifies that you can see through non-magical weather, but that obviously doesn’t cover solid fog, and freedom of movement probably covers solid fog’s movement problems, but that’s about it.
So solid fog might be better than wings of flurry, though against a spellcaster who can cast dimension door and/or freedom of movement you might prefer wings. And, for that matter, neither solid fog nor wings of flurry is the most unreasonable spell I’ve mentioned here—that would almost-certainly be freedom of movement. And that’s not even getting into stuff like divination and scrying, which provide no combat option at all but are incredibly campaign-warping when used well.
Of course, the context in which wings of flurry came up recently on this site was where we were considering extremely high caster levels. In that context, wings of flurry can definitely become broken—hundreds of d6s worth of force damage in an area is very unreasonable at any level.
- Improved evasion says that when you are subjected to spells like wings of flurry, that offer Reflex saves for half damage, you take half damage if you fail the save. So someone with improved evasion takes half the listed damage from wings of flurry on a failed save—but is still dazed for one round, since they failed the save and improved evasion says nothing about non-damage effects of spells. A DM may allow improved evasion to treat the spell in all ways as if you’d passed the save, but that would be a houserule. Also, since improved evasion is relatively rare, mostly found at high levels in classes that have a lot of incentive to multiclass, and moreover people who have it usually have very-good Reflex saves to begin with, even with this houserule it doesn’t change the conversation very much.