I loved Nihilus when I got him early via shipments. At all star levels.
But, I had left the game and came back, so I was far from the top of my shard.
I tried to get SiT later, but at g8 and 3* he felt as tough as the tougher members of the team (DN, DV, and if Palp was regening under DN lead, Palp) but without any of the damage or other perks.
In hindsight, sticking with him and gearing him more probably would of helped big time. But that's my experience from someone who's not far ahead of you (in arena strength, kinda bigger everywhere else). I've heard great things about him. But also he doesn't work that well alone with how easy it is to get around one tank.
To summarize, DN should work, no experience with Sion (duh) but I'd try it, dunno but doubtful about SiT.
Also, you've got a lot of your better speed secondaries on your arena team, but at first glance Ezra and Rex could give a couple up.
