Experimenting with combinations/unit sizes
You may find that its not the units that are affecting you, its what combination you take them in. It may be that you have more luck with bigger or smaller units. For me, a larger unit of raptors will be the way forward. Whilst five did well for me in their first game, they died just too quickly. doubling the unit size will make them more survivable. If you're downsizing units, you may find that you can make more use of transports, increasing mobility. Inversely, bigger units will be great for holding objectives and fighting in close combat. Either way, your theme remains, since you are utilising the same models, just in varying quantities.
Hopefully, these tips will help you develop and flourish with your cool themed army. I'm also going to practice what I preach, and inform you all of the changes it's made to my gaming. Check out on the Facebook page by clicking the Bonus Content Button/