Genestealers have greater mobility and many points of entry. When you become surrounded, use Command Points and place two of units back-to-back. The Overwatch command is more effective with more range, thus this formation works best with maximum distance between you and the enemy. Kite backwards and shoot your pursuers, even though it costs double the Action Points. Try to keep as much distance between your units and Genestealers. This will allow you time to recover from weapon jams.