If feel that this isn’t going to have the effect they want it to and it’s going to make clipping the channel pretty much mandatory to avoid any gaps in the bonus unless your latency is perfect (or someone makes an addon that calculates the perfect time to recast).
While I don’t really have a better solution off hand, I think that tying the reduction to the actual damage pulses would be more likely to push players in the direction they want & is more intuitive.
Edit: I just did the math on this.
This still creates a counter intuitive situation for the class.
The maximum CDR for disintegrate channels is 50% of the actual CD time (15s). Assuming a starting duration of around 23 seconds (rage(18) → surge(+4-gcd) → breath(+4-gcd)) that means we will need to fit 6.5 fully channeled lasers in the burst window for a second round of casts. With my current haste my channels are 2 seconds start to finish. This means that for every full cast I reduce the CD of the two empowers by 4 seconds. This means that to get the full 50% reduction I would need to cast 7.5 disintegrates. To get that many casts I would need 4 essence bursts, which means 4 other casts during the window. If we assume these are azure strike that’s +5s at my current haste. We can reduce down to 6.5 casts here as a result.
If I had 0 haste the channel time is 2.4s. That’s 6.25 disintegrate casts. Each laser reduces the CD of the spells by 4.8 seconds. The GCD would be 1.5 in that case, and you would need 3 essence bursts (or 4.5s) which reduces the overall laser casts to 4 and a bit. While the dps is lower in this situation (showing haste is still good) it creates a kind of back-flow where you have to work harder as you get more and better gear to get the same result.
To summarize that mini-thesis: Getting more haste will make dragon rage extensions feel worse to play than right now. My off the cuff thought of tying the reduction to the damage ticks instead seems like it might actually be the right call if they want to prevent us from clipping channels because no matter how fast you cast the number of ticks stay the same.