Hi!
I've actually been switching between magus and cinderhulk. I like the cinderhulk more because it gives me a better chance to survive ganks, especially when you ult in and such. It seems you're building a supportive jungle (with banshee's and frozen heart). I usually build cinderhulk > zhonyas > then situational items. The zhonyas is also needed for survivability when you gank or in general team fights. I put 2 into W then max Q. The W helps with jungle clear and power farming, but my Q is the main damage since it has a low cooldown and pretty easy to hit (if you play Diana a lot). Maxing W seems pretty safe though, and it can work well with cinderhulk. I guess the caveat to that is the high cooldown. Also for the smite upgrade, I go for chilling smite because of the slow. The burn from cinderhulk damages them, along with your W, so there's just plenty of damage that you can deal just by being close to them. It also helps proc Diana's passive. I've been playing Diana since season 3 and used her for jungle to get to Gold V. Not very high, but I just like playing Diana and would love to theorycraft with her. (:
