I have this account.
It has 2 legendary and some good epics for PVP / PVE
I would like to change it to an account with the penguin and another legend. Since I never touch the penguin 
Account level 9 in Elite League
Reroll till you get him. I know it takes a lot of time but it’s worth it. I had the same situation as you have, had 4 legendaries and they weren’t that good. I rerolled for penguini and lately I’ve got so much luck. Atm I have exactly 10 legendaries.
I’m not lying when I say that a month ago I’m trying
In my main account I do not have to Penguini but I have Soulstealer, Tiamazus and CyberDragon. Now pass me the story offline and online (God borrowed)
So now I try to change this new account by other similar,
surely someone likes Shadowing and Tiamad, are very good for PVP. I’d give anything to have Shadowyrm in my main account, It is just great.
Your legendaries are not even that bad, if your lucky you may get a last biter later in the game 