You need some support with ranged weapons fire. Stealers are fast, and you have a fair few of them, so you could probably drop any tanks you face eventually, but a lot of stealers would die first, and they're expensive. Drop a few stealers and replace with perhaps a few zoanthropes.
Frankly, the idea of an army made solely of genestealers is disturbing, depending on what enemy you face. Against Necrons... *shivers with glee*