Personally there is no need for one as if protection is what you are worried about then all you need is an umbrella insurance policy along with the insurance you get already, you should be covered.Good luck

You need to structure it correctly if lots of rentals.If you hold properties in your own name, then get umbrella liability insurance (worth your net worth) in addition to the normal insurance. 

I've read up on $2M umbrella policies and putting properties in LLC's, but at the end of the day, do I really want to deal with all this just to have a different type of investment in my portfolio?

My CPA advised just getting an umbrella policy when I first started to cover my rentals. 

I've seen topics posted with a title of "Umbrella Policy or LLC" on various forums.It should never be a question of one OR the other.Remember, insurance is like the Archers & Knights that defend your castle.You still need your Castle Walls and Moat for a well rounded protection strategy for what is inside those walls.

And research an  umbrella policy.

And make sure to account for the following expenses:1) Mortgage 2) Mortgage insurance (PMI or MIP) or FHA Risk base3) Property Taxes 4) City Taxes5) HOA (Home Owner’s Association) Dues and Fees and Assessments 6) Insurance  a) Property Hazard Insurance  b) Flood Insurance   c) Earthquake Insurance   d) Umbrella Insurance7) Vacancy Rate (usually 8% - the equivalent to one month a year, or 5-6% if multifamily and/or if experienced, if not use 8%)8) Utilities (you’ll have these if your tenant is not covering them and/or during vacancy)  a) Water § Sewer § Garbage  b) Electricity c) Natural Gas d) Propane9) General Maintenance (usually 5%)  a) Upkeep § Landscaping  b) Snow removal  c) Repairs   d) New Appliances 10) Capital Expenditures (usually 5%, higher is the property is old and obsolete, less if fully rehabbed and all mechanicals and roof are new)11) Property Management (8%, even if you self manage, your time still has value and there might be a time when you'll want to be completely hands off or you'll not be able to do it, vacation, retirement, etc.) 

I'll be calling my insurance company to look into an umbrella policy as well.

(This is in addition to liability and umbrella insurance coverage policies).

And lastly, myself, supervising remotely from some tropical beach with great wifi and delicious fruit cocktails with little bamboo umbrellas :)