Most things are optimal on a defender, primarily because you need less slots to do the same (defense, resist) with their higher bases.
I find defenders boring and have loved scourge since cov launch so I lean that way personally.
In terms of blasts, it depends. Sonic blast is definitely better on a defender, for ecample.
1. It's okay, cuz youll hit it even if you forget hasten and dont have it with 100% as long as you had it for a few seconds of the CD
2. It's inconvenient because if you want to AFK youre boned
3. You can switch your flashfire slots to something easy like Positron blast 5x and get 6.25, putting it to 89.89
This character that I’m thinking of (though I have some non giant ones with the issue) does have a crab backpack, but the female costume is the same identical costume for slot 2 and it has a slime aura, and this one in slot 4+ has no aura option.
There’s just no aura at all - in fact one of my characters has a female version /costume with the same costume, but he can’t choose an aura and she has one