On average- are investment managers worth the money?

If you need guidance, yes. If you just prefer to invest in index funds, no.

If you don't know how to or (more likely) have time to, manage your investments, yes. Usually there is a semi-managed option which costs around 1.00%, then if you want to get more complex you can start paying more to get more specialist attention.
What you are willing to pay is a function of how much you have invested and how much you stand to loose... if you invest $1000 then its probably not much value because your gain is only around $100, but if you invest $1,000,000 then the fee becomes worthwhile because compared to what you can gain, its small.

Yes and no, it depends on their qualifications and how their paid. For myself they would need to be either a CFP and or a CFA. There is two basics ways they receive income, either they are fee only or fee based. A fee only adviser gives advice on the investment product and doesn't make any commission on the investment they offer. A fee based adviser gets both a fee and a commission on products sold. To learn more about fee only advisers go to The National Assoc of fee only Advisers website.

Now if you make less than $100K I'm not so sure if you need an investment manager, just a thought.

Most fund managers can't beat the SP 500 (SPY) over the long haul. Some are even corrupt like the problem that happened in Australia during and after the tech com bust of 2000. Just buy an ETF or two instead.

If your the type of person who prefers to pay others for work they can do them selves.. then yes. They will of course try to steer you towards what will make them and the company they work for money and if you get lucky thats good for you.