I don’t have Sif. But I am surprised she gets tons of love. I mean, she is just an improved holy legendary version Boril (not the riposte though since hers is inferior: % damage reflected and number of turns). All her skills (riposte, damage reduction and mana generation) are dispellable. And purples don’t lack a ton of them in Kage, Seshat, Domitia and Sabina. When she serves as tank, she dies in not more than 5 tiles using monopurple. When she is flanking, other dispellers are aplenty, i.e. Melendor, Caedmon, Sonya, etc. Maybe she is good when used in attacking. But maybe I am missing something.
Among your yellows, I would ascend and max Vivica and her costume. Good offensively and defensively. She doesn’t deal damage, but her regular defense debuff is higher than White Rabbit’s. She and your Jackal would be lovely against purple titans. I’d also finish maxing your Gullinbursti and a second Jackal. Maybe you’d do those epics first. They wont cost too much.
As to your greens, I find Chameleon niche. IMHO, I don’t like wasting 4* ascension mats on heroes you would only seldom use. I do agree that he may be usable on 5* raid tourneys where blues are absent. But how about instances when greens are prohibited on 5* raid tourneys. I think he would be awesome on rainbow attack setup accompanied with ideal heroes, or 5th or 6th war team when you are depleted of the strong hero against the enemy tank. Among your greens, I would max either or both 2nd Hansel (you can’t have too much mana controllers) and/or costumed Little John (dodging is an awesome skill/ability). But if you have Kadilen’s costume, she is a must to be maxed and emblemed.
Among your red legendaries, only Mitsuko and Gefjon are the real contenders. QoH would be following after both of them, especially if you have obtained Puss or havent gotten Black Knight. I’d also max a 2nd Wilbur and a 2nd BT and his costume. They wont cost too much also. Them dupes maxed would come handy to you.
On your purple legendaries, I am more inclined on your Myztero. Having 3 distinct very fast legendaries would surely wreak havok with your Kage dealing the maiming initial damage (if the target did not die) leaving your Clarissa and Myztero dealing the finishing blows. I would also finish maxing your second Rigard, too.