If no one told me about the changes to Frozen Orb there's no way I would have noticed today after playing for an hour or so.
The changes are mostly a compound effect of the typical spec, not just Orb itself. Even if you aimed your Orbs--I didn't actually know people just blindly spammed the screen without aiming until I was informed on Battle.net that "everyone" braindead speammed--the explosion was rather large, and would easily hit many enemies outside of the path your Orb was travelling. 2-3 straight shots of an Orb and you could decimate large packs. It's not quite that easy now. The radius of the explosion was radically cut.
On top of that Cold Blooded now last for less time. This isn't really that much of an issue if you're constantly spamming Orbs on your target, but it does mean that in conjunction to the reduced radius of the explosion, more enemies end up unsnared and without the damage debuff much earlier than before that are on the perimeter.
The main thing that hurt the spec though was the change to Electrocute and Prodigy (they also nerfed Mirrorball, so the returns on that are dead too) in regards to Arcane Power gains. You spend a lot more time using your signature spell than previously required. The spec isn't dead, and it still kills things well enough, but it's definitely nowhere near as strong as what it was.
The irony is that some Demon Hunter specs were already as good as the FO build, and they just got a few buffs.
I just said "fuck it" and decided to finally go Disintegrate. Had been meaning to for a while anyway. It was better than Orb as it was on anything higher than T2. Its main downside was that it was less mobile; but you can just run past large packs now and go turret mode, instead of casting as you move like with Orb. If you were already using Archon (many FO builds did), it just gets even better in a Disintegrate build.