My question is simple. What is my portfolio missing...
Simple question. Hard to answer.
As someone else said, get what you can into a simple or Roth IRAs. What you already have is a very typical, solid balance. Do nothing and you're very likely to do just fine.
Everyone here has a different balance for diff. timelines, goals, risks, etc. and most of us are doing real well despite doing some very different things.
To me, the Total US Market Index is a foolproof, starting point. And you have a large chunk of that. Anything else IMO is just a way of trying to 'tilt' your risks/goals/timelines/predictions. That's what your Europe/World-ex.US, Bonds and REITs are doing.
If we call those 'holes' that you've filled, there's also stuff like Gold, Emerging Markets, the high flying Oil/Tech/Health Care sectors, etc. that could fall into that same-ish realm of 'guessing game'.
You might want to think about dividing your 40% that's not in VTI into some of those other risks, but then I'd suggest just focusing on VTI instead to make life simpler.
Personally, I like VO -the Mid Cap Index instead of VTI. I think it's a safer/better guess at tilting your investments up over VTI alone. So then I don't bother with much of those other things I listed. VO consistently follows, but beats, VTI and is only a touch more volatile.
The research on Bonds seems to be that long term, they just make you feel safer while you earn less money. They don't really 'counteract' the market like people seem to act like they do. REITs follow the market, but have lagged. Gold is a total guessing game, but doesn't correlate with the market. Europe follows the US market and used to better it, but now it lags, so might as well go with US Mid Caps which have always been better. I think Europe still has long term problems getting over the 2008 crash. I've gotten burned on trying to get in/get out of Em. Markets, but looooooooooong term, they should be winners.
Also -the point of your dated retirement 'fund of funds' is that it's suppose to be the only thing you own. Anything else messes up the point of having that pre-made balanced investment portfolio. Much of the other stuff you have is pretty much what that 2050 funds contains, though, so there's no real 'damage' in your case.
But, if you can, I'd suggest you get rid of it. If you can't right now, you could just try to re-adjust the rest of your portfolio so that it all acts like one total 2050 fund (if you like it that much). Since you have REITs, it shows you actually don't think the 2050 fund is the perfect total portfolio for you.
With all the pieces separate, you have full control to re-balance all of it.