I always choose slice 5, the 6 pm ending time make it the only sensible option. I went with CL8, so that I have some idea of what's coming in the future.
I have no 5* over level 310, my best 4* are around that level, and I'm seeing nodes that max out about 50 levels higher than I was seeing before. But I don't really care. As long as each event has someone boosted that can one-shot or nearly one-shot the worst of the opposition, it doesn't matter.
In this case it's 4* Iron Fist, whose black does about 28k damage. He and 4* Blade and Cloak & Dagger have made this event almost a walk of cake. I should make top 10, unless real life commitments this evening get in the way. And that would be better than usual.
:edit: #7. I is content.