Okay, so we all know that each card you use that's Staff Banned in ELO takes 2 points away from battle. Now here's the question to you: does help you or not?
If I was ever asked this, I would say yes. Having a GraksmxxT of Caelus makes your opponent more alert, watching your moves, thinking you'll KO with that card. I love it when I knock someone out with a surprise KO without using my Caelus at all.
You need to do some math to see if it's worthy of keeping those cards on your deck.
Jackie is, because she is a 4 stars with the stats of a 5 starred card.
For a win, you'd take 2 points away from you because of Jackie on your deck, but if you consider him to be a 5 stars card, you just lost 1 point. If you won a round with Jackie (which is pretty easy to do ), you won that missing point if you compare it with a 5 stars, so there is nothing to lose here.