CoC Ice Nova of Frostbolts Harbinger?

I want to play the new Harbinger ascendancy on Witch at some point, simply because being blue and able to fly sounds kinda fun.

https://preview.redd.it/x4ram96u1ije1.png?width=3840&format=png&auto=webp&s=6ab64e2409735ad4f0ff8835a9bd85dfe235d740

But the ascendancy really doesn't have much going for it, you basically always take the 40% cdr, 30% faster/slower expiration and most likely the free temp chains aura node, then put in one of the harbi skills, since you cannot have more than one of them at the same time. The best harbi imo is the focus one, which gives immunity to curses, stuns and all ailments, plus 20% generic DR, which is pretty goddamn strong but it only works with channelling skills.

One thing to mention, with the cdr and slower buff expiration you automatically get basically 100% uptime on the focus harbi, because duration goes up to 5.72s and the harbi's cd goes down to 5.71s. With just a tiny bit more duration or cdr it'll be a literal 100% uptime.

Thinking about possible skill choices I quickly landed on Cyclone coc, I mean 40% cdr from the ascendancy makes getting the 52% breakpoint very, very easy and you can make full use of the harbi buffs. Mostly I just want to see what a harbi cycloning around would look like, sounds hillarious to me.

So I've been looking at the coc meta, I haven't really played any ever since the 3.15 mana changes. But it seems the meta nowadays is mostly Ice Nova of Frostbolts with Cospri's I guess? So I've been clubbering together a basic template to cap crit, aps and accuracy and landed on this: https://pobb.in/6si60Rjeq_eS

But as I said, I haven't played or even looked at many coc builds ever since 3.15 so I'm really not all that sure how to scale and what to go for. Having to rely on flask and brittle ground to cap crit for examle sounds pretty annoying, so I fear Mageblood would be kind of mandatory. That's not a problem though, just means I'll play this a bit later.

So in short: how do I effectively scale the dmg? And what to go for defensively? Seems most people go LL on Shav's but how does it compare to CI? And what do I go for beyond ES? maybe just go for Svalinn? Or maybe even forgo Cospri's and go for a giga crit and aps rare with crafted "hit cannot be evaded"? Would probably have to sacrifice a link in the coc setup though, so I'm not entirely sure about that one.

And finally: is it even worth it? Or would it end up as just a worse version than Occultist? I mean one thing that speaks for harbi is all the defenses you get, simply solving literally any and all "status ailments", stun and curse immunity with one click and even getting basically a better fortify on top is not to be underestimated. Though I'm pretty sure "damage reduction" would scale additively with endurance charges.