Part of the reason why I benched Scarlett is because she’s just too damn squishy, even more so than Jackal. Jackal at least is very fast so can usually pull off one shot before he dies, can’t say the same for Scarlett unfortunately. I stopped using her in raids because she doesn’t stand a chance against emblemed 5* (unless the board is good, but then I could just as easily replace her with someone else and still win), and even against +20 4* she’s kinda iffy, so I don’t even use her in 4* tourneys anymore. Only place for her is on titans, but once again better keep an eye on that HP or use Wilbur frequently otherwise she’s going down in 2 slashes.
Yes her tile damage is insane, but other than titans that really doesn’t count for much because a dead hero is a useless hero. Marjana desperately needs more attack to take advantage of that huge 458% multiplier, and she’s already sturdy enough so emblems seem to have more utility on her.
As far as the +8 mana boost node, I’m personally not a fan because the long term goal is to get troops to lv 23 (or 29 if you play long enough/have deep pockets), and the rogues in question are all very attack-oriented, so the alternate branch with +HP and + atk seems much more appropriate.