Ok, so, playing around with it on the beta, it’s an odd ability. Warning, this is a bit of a stream of thought as I did my testing.
First off, the tooltip in-game is inaccurate. Going from naked to just equipping a vers/mastery ring (it deals Chaos damage) changed the tooltip ratio between it and Unbound Chaos from 0.79 to 0.74, which shouldn’t be the case for two chaos damage abilities.
I abandoned tooltip analysis as a result. Naked except for a pair of itemlevel 75 glaives (premade DH, because at one point transfers weren’t working for them, and I’ve been too lazy to see if that’s changed), it deals 44-47 damage per tick, for 14 ticks, which is approximately 190% as much as Chaos Strike deals.
Assuming there’s nothing funky going on with that ability’s math, that puts it at around a 120% AP coefficient. However, there is definitely something funky going on with the ability’s math. Naked, it deals slightly more damage per tick than Trial of Ruin (45.6 versus 44.5). In full premade gear, it deals quite a bit less (93.5 vs 109). From testing, the tooltip and damage are not currently affected by mastery, though they should be.
This puts the AP coefficient at ~150% AP, based on ratio to Unbound Chaos’s damage after factoring out mastery. That’s actually quite strong. Assuming it will scale with mastery, it’ll deal, per tick, about 131% as much as Trial of Ruin. It gets in 14 ticks per 20 seconds (or maybe 13, it was a bit inconsistent), and Trail gets in 4 per 9s, with both cooldowns scaling with haste. This puts Glaive Tempest as providing more than twice the damage of Trail (and by extension, Unbound Chaos). Also means it’ll be useful even in single target, and that should be true even when they inevitably tune it down to balance.
It does have some odd effects, though. For one, it’s probably completely incompatible with Momentum. Turns out if you leave melee range, it instantly stops dealing damage. Also, while the cooldown scales with haste, the number of ticks do not (which is justified, since the CD does. Means it doesn’t work like a DoT, though).
Our AoE burst also got dialed to 11 by this. Eye Beam + Glaive Tempest + Fel Barrage is pretty silly.