The flash/diffuser set-up that I use is only good for close range work, the further out the subject is, the less benefit the flash is.My bee pics aren't technically macro, since they are heavily cropped. I usually use my 18-55 for bees and bugs. I'm wondering how flash would affect them? It's usually bright and sunny when I'm out snapping pics. Using flash has never crossed my mind...
Thats not saying you couldn't make it work, you just have to adapt things to your needs.
The best way to see if it will work, is give it a try, and go from there.
Start a thread, post photos, and ask for help if you need it