If the 2D Stuff you are talking about is Textures for 3D Models... 3D Coat certainly will give you a good paint mode, with layers, blend modes and brushes.... filters IDK, but then those usually are not to be found outside of specialized image editors.
But out of curiosity: why are you looking for the swiss army knife that gives you a too small and weedy saw, and a a too small and incorrectly shaped knife, instead of getting a real saw and a real knife that would be tailored to what you need? Because you think learning a tool with so many bells and wisthles is easier than learning 2 tools?
Let me tell you this: find the tools that are best at the job in your price range, and if that happens to be a NURBS tool that can only be used for NURBS modelling (MoI comes to mind), so be it... if it helps you shape a complex rounded mechanical part in record time, and you need to do a lot of these, it is worth learning an additional tools interface (especially in the case of MoI, its one of the most intuitive 3D apps I have seen yet).
For 2D work, get Gimp as your freeloader jack-of-all-trades package, have a look at more specialized apps for specialized tasks like Manga Studio / Clip art studio for comic drawing (its quite cheap and very powerful, and actually very useful outside of comic drawing... that brush stabilization is a goodsend both for people with unsteady hands AND people using crappy digitizers!), or if you really want to go pro, or are a student, get a license to Photoshop...
Sketchbook Pro is also pretty cool for light sketching, and not too expensive, but also more specialized than PS or Gimp.
For 3D work, Blender can do it all. Somehow. You just need to crack the user interface 
... personally, there are reasons why I turned my back to Blender, Maya Lite is a good way to get a tool with less limitations than Blender (but also a quite quirky interface)...
In the area of more specialized tools, you get ZBrush, 3D Coat or Mudbox for Sculpting, and Texture painting, MoI as CAD Lite / NURBS tool, DDO /Quixel Suite and the Substance Designer / Painter for procedural PBR Texture creation.
Really, these are all extremly powerful tools for their specialized applications, Gimp / PS for all 2D work and Blender / Maya for all 3D work. The more specialized tools are more narrow in their application, but also more powerful or efficient to use for that.
Finding a good Jack of all trades that combines 2D and 3D sounds like an impossible task. Don't think such a tools has been created yet, and I somehow don't think such a tool makes much sense.
I used to think I would be better if I just had a cintiq but I ended up getting one and I still suck. It doesn't matter what program or special tool you have its all about whos in control of the pen.
Well, I have to preface my statement here with that I have some expierience with drawing and while not being a pro at all, I am also able to do SOMETHING with pencil and paper (given enough time :) )...
But my Cintiq has been my best purchase of the last 3 years! Granted, before getting my current 24HD, I had a 12WX, which was quite an underwhelming expierience to work on... too small, to dark screen coupled with a just not quite accurate enough digitizer... bleh.
The 24HD on the other hand couldn't be more different to handle. A well lit screen, big enough to comfortably work on, and the digitizer is quite accurate... and thanks to the big screen real estate, the usual wacom digitizer edge inaccuray bothers me much less than with other wacom digitizers I own!
And really, being able to work like on paper, but with the ability of unlimited erasing (without the paper turning to a muddy grey or just getting shredded to bits by the eraser), and having layers to work with, has really helped me getting better with 2D art.
I personally think the problem with cintiqs is that the small ones are just too small... 12" or 13" sound like a lot, but after you subtract some area around the edges that are not really usable as the pencil gets inaccurate there, the usable area is even smaller than an A4 sheet of paper. That is REALLY small. Most artists working on traditional media I have seen seem to work with much larger pieces of paper (or whatever media they use)... I wouldn't advise picking a cintiq below 22" as long as do not need a mobile cintiq.
But long story short:
I agree with your statement that its first and foremost the skill of the user, with the caveat that a skilled user might be able to dig the same hole with a shovel than with an excavator, but he will spend 50x as long doing the same work.
Better tools usually make you more efficient at the task, but seldom allow you to create something above your skillset. You will most probablynot be the next Michelangelo, even with the best cintiq and Corel Painter Software. But imagine how much quicker Michelangelo might have completed some of his masterpieces with the proper modern digital painting pipeline in place!
