Many folks would say that bonds are for stability when it hits the fan. They should be steady eddy things. Thus, those folks would recommend that you only need US Treasuries. Anything else is basically taking on risk that you should take with your equities. You can do only one more thing: Control the duration. So you can have short-term bonds and intermediate-term bonds.
What that means from a practical sense is that one does not need high-yield bonds at all. One can get the same risk/return characteristics of high-yield bonds by buying US Treasuries and an equity fund. So if you have 10% in high-yield bonds, is that not the same as have 5% in US Treasuries and 5% in the S&P500?
The same goes for international bonds.
TIPS are nice, but not at current real yields. You might as well go to shorter duration bonds which already have inflation-changes priced into them. Longer term, a retiree might want TIPS, but they are not safe if you have to cash them in before maturity. If real yields go above 2.5% and 3% like they did in late 2008, then TIPS are a buy.
Some folks would avoid even total bond index because it has some mortgage-backed securities in it and intermediate-term corporate bonds.
So I use a total bond funds and short-term bonds funds. I don't need to get more exotic than that. I take my risk on the equity side.