Join Date: Jan 2009
Location: Worcestershire, UK
In my experience its very rare for MCs to get cover saves from being obscured, in those cases where people try to claim it it is normally pretty marginal and would normally be downgraded to a 5+.
Personally I like to get my cover saves by making mixed units: hive tyrant with guard or tomb spyder with scarab swarm. That way you can get a cover save on the non-MC for intervening models or being in cover and pass it on tot he MC (if 50% of a unit is un cover they all are).