Common sense would not say Sylvanas, she is lead by emotion at times too and that is definitely one of your negatives for Jaina.
Common sense would say her cunning would not allow her to say “The Horde is nothing!” just because Saurfang gave her a shpeel about the Horde being strong and her failing all the time in his eyes, that’s being lead by emotion more than anything. If she wanted more death she could have simply said something that she embodies the true strength of the Horde and then blasted him in one hit.
No, Sylvanas is “cunning” because the story is written for her to succeed at her “cunning” aka plot armor