Mycurlytresses, I can relate to the Eco Styler fail. I can't use Eco Styler in any form, including the one w/olive oil. I think it's all the glycerin.
When excessive stylers are used but over time the hair still doesn't have the kind of "hold" that's desired, or the "frizz control" that's desired ... and especially if after all that, a diffuser - which is a pretty mild current of air - still drastically changes the behavior of your curls from their wet to dry state, the desired look might not be compatible with the way the hair itself wants to naturally behave in its dry state. ... Someone else may come along w/a better explanation though. If I'm wrong and the look you want is achievable, I think that will be fantastic.