The two immediate things I see (presuming you're focused on keeping Hellions in your list

);
1. I'd advocate splitting your Reavers up - they are fragile enough that the firepower it takes to kill 3 would pretty much deal with 6 as well. By splitting them up you force your opponent to have more units dedicated to dealing with them.
2. Are the Sybs really serving a purpose? That's some easy points to save right there, and without bringing upgrades to them I rather question what their purpose is, especially since those points could go towards something like FFs - which help prevent the only thing you'd really need the Syb for, and that's leadership after a vehicle is popped. I'd say go with the proactive, not the reactive defense.