Yes, there's the same problem on my android tablet.
I think it's the 4:3 aspect ratio.
There are similar issues around the game like in the arena battles and the arena opponent list, where the right part of the screen is truncated
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OK, same for me here, 350 skulls and SQ still locked. I hoped the daily reset would have fixed it but ... no
It doesn't seem to be IOS related because I'm playing on Android.
Hope it can help for the investigations.
Imo, best team for farming the challenges: IE/Magus Ninja/Gunner Ninja. Load up on energy talismans. Gunner ninja creates the crave, IE turns is it into Toxic burns. Gunner Ninja reduces fury with basic. Magus Ninja smashes out heaps of burns. Plus they look cool fighting together ;)
Update: The skull quest is now open for me and it seemed to open for me once I completed final level of Hard even though I was already way above the requirement for it to open - good quest for rewards it is too!
I quite like Killer Eddie too - he looks like he should and he has a decent skill set - need to figure out what best to put on him but he is up as my Champ for now if any of my Troopers want to try him out. I stuck Explosive and Purge on him for now.
Cheers