Just did that to a star today. yes its a pain for them - they can plan around it and make sure all their guys are split up - but it will slow them down a turn and if you force them to voltron out early - you can pick off each part quickly - especially in swarms of dogs and without FNP etc. But it works really well - tested Tetrad plus Daemon CAD - went with Tzeentch DP as the Warlord.