This is the exact same makeup for my pve group as well (warrior/priest 2 mages/lock). I am having a great time playing this group as well.
Before I started I had doubts about being able to play this group but it really isn't that hard at all.
CC works great since with focus you can set it before a fight. Having a lock instead of a third mage is def a good idea and doesn't make anything more difficult really. The only real challenge with this group is dealing with healer aggro I think. Maybe a druid or paladin would be easier with this I'm not sure I have no experience of them. This is my only nagging doubt about this group is what is the best tank.