He seems to sometimes be going incredibly long periods without casting it, something I can’t find in any video or recall in my own experience.

Example

00:00:55.502	Kel’Thuzad casts Frost Blast on Chewy
00:02:32.975	Kel’Thuzad casts Frost Blast on Soildsra

A full 1m37s without casting his ability that clearly has a 25 second cooldown since other times he’s casting it every 25 seconds.

I suspect it’s something to do with batching so he’s missing a cast and resetting his timer somehow.

Also less extreme examples

00:00:34.982	Kel’Thuzad Frost Blast Kiwiandapple 1818
00:01:45.867	Kel’Thuzad Frost Blast Kiwiandapple 1817

00:01:48.692	Kel’Thuzad Frost Blast Kiwiandapple 1818
00:03:07.292	Kel’Thuzad Frost Blast Leps 1738

If we look at something like this

Frost blast at

5:46
6:25
6:59
7:28
7:56
8:22
8:48
9:33
9:58
10:30

Kel'Thuzad's ability use on PTR