I run an empire team and have wondered the same thing. My vader, boba, B2 and Zylo are maxed. I run EP lead and am waiting for the Ep event to get his 7th star. I have finished #1 in my shard for the last month. I don't know who I would replace for Nihilus. I've thought about Boba but he's so useful with blocking, execute and adding dots for Vaders CB.
I'll say this, there aren't a lot of people running Wiggs anymore except for people that have high level Chaze. Because of that, I don't even use my ShT anymore.
