Wait, what do you mean Tara is out of the picture? There's still like 15k CS of Tara around Leohampton. (Which, I might add, is just barely over the size of the force that was typically helping Coria. I'm wondering where they squeezed out that extra 2-3k CS when we heard a lot of excuses during the actual war.)
Quite simply: Coria wasn't worth the extra effort. Carelia is, and Minas Leon is.