You’re both right that their hand was forced by the contractual issues. They really bet on the wrong horse with this story because it’s absolutely dominated the show over the past few months, and they’re left with… this.
Tara was such a dreary miscast that I can’t imagine this being drawn out for months and months. (I feared they’d latch her on to Jack to save the character. Glad they weren’t that invested in her.) Usually, low-energy actors spark when their characters go from good to bad, and EL still flatlined every scene she was in after Tara went full-on villain.
They could have had Sally target Nick, but if they’re going there, they’re doing a pretty crappy job of moving in that direction. This is the second or third time this year they’ve had to bail on a story because they had issues with the cast (the Chabby marital drama surrounding the baby being the other, and we see how they’ve tried to salvage that one).