I don’t really agree with the OP, because I’ve played Zane a lot, and he’s definitely had a very identifiable niche and playstyle for me. Actually, at least two of them.
For most of my history with Zane, I’ve played him as a Cryo character, with Cool Calm & Collected replenishing my action skill every time I freeze someone, which is just about all the time. There are so many cryo-based skills, weapons and items in the game that when you combine them all, you’re basically a walking snow machine. And since 2 of his action skills are hugely impactful (clone and barrier), being able to almost constantly replenish them by skillfully playing freeze tennis with enemies is very rewarding). Aurelia was my favourite character in TPS, but Cryo zane has been even more fun, and definitely more memorably unique.
Oh, and I’ve never used Seein’ Dead (I don’t really see the point - I’m killing enemies all the time anyway, so I don’t need a COM to trigger kill skills). I’ve mostly used Cold Warrior, which adds damage to frozen enemies (which is basically all of them).
The other main playstyle I’ve used with Zane is a clone-based one where I’m constantly flanking enemies by switching places with the clone. This is fun - and actually a bit tiring to be honest - because it takes so much vigilance and quick thinking to do well. It tests your spatial intelligence and concentration skills, but done right, you’re like a lightning-fast ghost: portaling around the whole map, almost never being targeted by enemies, almost always shooting them unawares; constantly diving into the chaos then escaping in the nick of time. It’s a breathaking way to play the game.
Then there’s a third playstyle which is almost the polar opposite of the previous one: the Barrier turtle, where you park yourself in one spot and try and blow away anyone who comes too close, using clone and/or cryo as needed to keep them away. I use this playstyle for bosses sometimes, though it’s obviously not the most exciting way to play. But it’s definitely a unique way - even Moze doesn’t feel this ‘tankish’.
So no matter how I play Zane, he usually feels very different from any other character that I’ve played.
Maybe the trick is to stay away from Seein’ Dead (which it seems no one on the planet except me does), since that COM leans you towards a more typical run-n-gun playstyle, and towards the least interesting tree - blue - which itself comes with probably the least interesting Action Skill in the whole game (SNTNL).