I think she does enough to get into the lower bomb range, especially because even if you dont have a deck with a critical mass of ETB triggers, the addition of shutting down opposing triggers makes it more likely she has a real effect in addition to the statline Her static ability alone does a pretty good job of protecting her, as taking down a walker with a single creature attacking at a time is quite the challenge, but her other abilities are also really good and make it challenging to ever take her down
Its an equivalent exchange you and your opponent go down 1 mana
The term "defending player" in the myriad rules (or any other ability of an attacking creature) refers to the player the creature with myriad was attacking at the time it became an attacking creature this combat, the controller of the planeswalker the creature was attacking at the time it became an attacking creature this combat, or the protector of the battle this creature was attacking at the time it became an attacking creature this combat
My tendency would be to lean on the Swords Sword of Fire and Ice, Sword of Light and Shadow, etc
Sword of War and Peace Sword of War and Peace isnt the greatest sword on the list, and while it doesnt change things up on the board, it does have relevant protection
Its essentially Cryptolith Rite on a stick that brings its own band