I guess DC 31 isn't so bad, but Rogues are still going to Pounce into its face and Evasion out of the blast pretty much with impunity it they're buffed and geared decently (though I guess the uncanny dodge is its own headache for them.)

Losing Polymorph really hurt here more than it did to a lot of creatures, because it added some much needed versatility to its one trick pony-tude. I can sort of picture a situation where the party can't kill it and it just follows them around with its 200 foot fly speed making a complete nuisance of itself, and it might be really annoying to deal with a horde of them all together or supporting a bigger monster or guarding a puzzle-trap, but its going to take that sort of a goofy situation for it to really shine.