You're talking about Flashpoints. The OP is talking about Heroics. Both are available in the GF tool.
And yes, it would be nice to use the Group Finder to get a group for a specific heroic. However, I would imagine your queue times would be very very long as it would depend on 3 other people queuing for that exact same heroic.
Just figured out OP was talking about daily heroic missions on planets, not Heroic Flashpoints. Which I also just remembered are called Hard Mode, not Heroic. Bad WoW reflexes. Bad.