Depends on the titans you are fighting. Aegir is great for titans, giving them staying power. I’ve been using him on all but Green titans (when I use Wilbur). The healing is just as valuable as the shared damage, making him much more effective than Wilbur for keeping heroes alive during titan battles.
Miki will give you better damage, but not help keep your heroes alive. If you are fighting 10+ titans, I would think that Aegir would give you better results all-around.
With your lineup, you could go Frida, Alice, Aegir, Magni and Miki, an un-emblemed Kiril is pretty useless for titans and Aegir will give you the healing you need.