D2-style nova witch build idea

So I remember the nova sorc in D2 that used a runeword with -res curse on its merc to wreck stuff, and had a pretty fast playstyle with tp and lots of fast cast, and I wanted to recreate sth similar in PoE.

Given the current bias towards cold in witch ascendancies I've used ice nova, together with tri curses for playstyle (I really like that everything's auto and I only have LMB and RMB - D2 style), safety and dmg as well as crit for a bit more oomph. Happy to get some feedback on gear / gems / tree below as I'm pretty far from having the encyclopedic knowledge required to think of everything.

Specific questions I had
- Is 90% too much critical chances that could be redeployed elsewhere skill- or gem-wise (added cold?)
- Is the defense OK on this? Don't know how to find more life and Acrobatics is FAR

Gear
- Doedre's scorn
- The Covenant as we're reserving 100% of mana
- Divinarius x2 (couldn't think of sth better, cheap)
- Kaom's root for massive life and don't really need another 4L

Gems
- Ice Nova - Spell Echo - Faster Casting - Conc. effect - Inc Crit Strikes - Inc. Crit. Damage
- Frostbite - Assassin's mark - Enfeeble - Blasphemy
- CwDT - IC - Inc. Duration - Phase run
- Stone Golem - Minion Life - Minion Res (to alleviate blood magic in The Covenant)
- WB - Faster attacks - Fortify

Tree
http://poeurl.com/cbuo

PoB
https://pastebin.com/MYbNd0x6

Bump