i must agree with you - corsairs are better to kill overlords than scouts..
but seems, through all text, You forgot that scouts can kill creatures on the ground :)
i never use scouts tho.. the best ways to win a terran:
1. fast rush(in maps like lost temple and python they want to wall-in, so go try to get in when u have 2 zealots 2 dragoons)
2. reaver/DT drops
3. let him push, expand yourself - "secretly" tech to carriers
4. good macro with arbiter recall wont even need to "break out"