DevaCurl is a love/hate thing around here, and you'll see lots of mixed reviews. I do still use Deva products, but none of the ones in the trial kit- I prefer the DevaCARE No-Poo and One Condition and Deva's new Ultra Defining Gel is one of my HG products. It could be the products, it could be your techniques, or some combination of both. A few things to consider:
Hair properties (texture, porosity, etc) have a huge impact on the types of products and ingredients that will agree most with your hair. If you haven't determined your hair properties yet, has tons of helpful info. Once you know your properties you can look for other people with the same properties and see what works for them. There's also a thread on the 2s forum (probably a few pages back) called "share you hair biography," which will give you instant access to potential hair twins.
My biggest issue with the Deva trial set is that it includes the Light Defining Gel. I found that it wasn't a strong enough hold and I ended up with frizzy and undefined hair. My personal observation is that people with weaker curl patterns do much better with stronger hold gels (a favorite for the FB Wavy Hair community is Biosilk Rock Hard Gelee).
In terms of technique, the biggest thing to remember is that the more you manipulate your hair, the more frizz you will end up with. I get extra frizz if I scrunch too much, or if I mover my diffuser around too much while I'm drying my hair. Some people do well with microfiber towels, but other people have better luck with cotton t-shirts to remove extra water. Just make sure you are gently squeezing and not rubbing your hair to remove water.

Modified CG since 11/5/11
CLEANSE: CJ Daily Fix, DevaCare No-Poo, CHS Treatment Shampoo
RO: SS Caitlin's Conditioner, CJ Beauticurls Strengthening
LI: SS Repairing Protein Treatment, CHS Silk Leave-In
STYLE: Re:Coil, Curl Keeper, Deva Ultra Defining Gel, Curls Rock Amplifier,Sweet Curls Elixirs Okra Gel and Hard Hold Gel, SS Curl Enhancing Jelly and Firm Hold Gel