Check out the fratenisation at about 115 seconds, both scanners get it on with the enemy.
Anyway... I've been experimenting with adding a WG to my psyker/sentry combi force. Though it's expensive I think it adds a useful area effect capability.
Deestan's hunters proved troublesome - they are fast enough to target my psykers. Fortunately he only had 4 and I could bury them in greys. Once they were out of the way I had complete control of the game. Tanks have no chance at all against a sentry/psyker force.