If you use a Cluster Missile with Marksmanship - the way I read it is that you basically get the focus on both attacks, with only the critical part on one of them.

Am i right?

EDIT - Never mind I just checked the FAQ - turns out it fully effects both attacks. Sorry for the wasted post.

No. Each attack, you may use Marksmenship, ie one (eye) fir each attack may be changed to a crit.