That is the lowest price I've seen Omnisphere 2.
The Groove3 course is very educational and worth the watch. Especially if you want to learn more about how sounds are made in Omni and make your own. I have an all-access account with Groove3 so that might be something you'd rather look into.
The Omnisphere sound bank is impressive in both size and quality but they do lack if you're looking for specific sounds that might not be the focus of the core library. I find that many of the sounds I use come from other designers like The Unfinished, PluginGuru, Audiority, etc. because they not only tend to focus on different libraries of certain sounds, but they also push the limits to what Omnisphere can do. For instance, The Unfinished has a few multi-patches that sound amazing but will completely wreck my main computer which is an 4ghz i7 with 64GB of ram because of the way they are designed, the amount of high resource gobbling samples and effects, etc. all in the one patch.
Many libraries tend to use the main soundsources that come with Omnisphere but you also have people like PluginGuru who will add in his own waves to build off of in his libraries. That also opens up another area of sound design.
Do you need to buy third party libraries? Not at all, but I suck at sound design so these libraries help augment what I do.
Is Omni 2 worth it? I use it on pretty much every single song I make so to me, absolutely. Is the bundle? Take a listen to the library they include
http://www.audiority.com/shop/relative-dimension/ and decide if that's what you plan on making with Omnisphere. If not, then likely not worth it. Especially when you can often get a few days of Groove3 for free now and then when they do promotions.