I'm pretty much DIY except that I get a (free) yearly financial consult with Vanguard. Most of my holdings are with Vanguard and they pretty much tell me I'm on track. I take that with a bit of skepticism because, although I trust Vanguard, I don't k now if they are just stroking me so I'll stick with them.
I got stiffed by two "financial professionals" in the past, so I have read all the books, done all the research, spent a lot of time on the web researching this stuff (which I enjoy doing). I'm pretty much an index fund investor at this point although I do have some fixed income holdings outside of mutual funds. With an inflation-aadjusted pension from the Navy plus SS (which I just started taking in May at age 62), I'm pretty comfortable with my 5% cash, 47.5% equity and 57.5% bond AA.
Being a military guy, I first got into investing through USPA-IRA (now known as something like First Command). They had sound financial advice (in terms of getting you to invest regularly and with discipline) but the investment choices they offered were designed more to generate commissions for them than to improve my financial security. But, sometimes, you have to learn lessons and I did from that experience. (I never lost any money through them; I just didn't accumulate as much as I could have if I had been more knowledgeable.)
The second "stiffing" was from Fidelity who convinced me to take money out of Fidelity mutual fund I had bought from the above company, pay the capital gains and put it into a variable annuity. The annuity (which I have long-since moved to Vanguard) has made a nice gain over the years, but the tax consequences won't be pretty. Again, I learned a good lesson.
Bottom line: I think the DIY method is the best (after you have educated yourself) but I also think an annual look by another person (who doesn't have a profit motive) is a good idea.