-then it would need to be at about waist level 
My thoughts exactly. You should try something like the Hügelkultur containers I make. Portable, easy height to work and harvest, and arguably the best way to grow leafy veggies that I have ever used....I think maybe some people do it because they think it's trendy!
The one time I see raised beds to be beneficial I think is when you get really old and useless like me, and have a hell of a job getting down to the soil - let alone getting up again
Regardless of the size that compost in place / wood core / Hügelkultur filling is the best way to build up a container.
I also really like @Meadowlark 's hugelkultur method, and I'd want some sort of buffer to keep the sticks and dirt together instead of sloughing into the yard (again, mowing). @gdgross I don't know if I'd go that high, though I hadn't thought about how much easier it'd be to not bend down....for my broccoli and such, I'd do that, but for the vertically grown ones like my beans and whatnot, I couldn't go that high...so I suppose I just have to weigh my options!There really is no limit to how high you can make a pile / hill / or berm but put some real thought into going much higher than knee high.
I just watched this video last night. I've been gardening for 10 years and thought this would be helpful for you.
Thanks for sharing that, very interesting
I have some wicking beds and really like the fact that they are self watering. What I've learned while using them is that water tends to only wick up about 16-18" so if you build a tall bed you'll need to use something like the hugaelkultur method to help hold water high enough to reach your roots. Otherwise you'll spend a lot more time and water on your bed. Here's a video that may help wth that. I like his new concept.
I couldn't disagree more, where I live rocks are everywhere and using raised beds is the only way I can grow veggies like my tomatoes. The soil in my beds is 20" deep and I plant my tomatoes 12-16" deep in the soil so they can develop the root systems necessary to support and feed my very large heirloom tomatoes.I really don't see the point in raised beds at all, all the time your soil is good. Even if it's not good soil, you just need to keep adding compost to improve it. A 4'' raised one would especially be a waste of time in my book. I think maybe some people do it because they think it's trendy!
The one time I see raised beds to be beneficial I think is when you get really old and useless like me, and have a hell of a job getting down to the soil - let alone getting up again
Preparing the soil is most important. Dig, break up, rake out to a fine tilth and pop in the seeds!
Well now, that is an extremely good, valid reason for building them,and there are clearly more reasons, but I did mention that I couldn't see the point IF the soil is ok. In your case it is not.
