I would seriously doubt any system that sees Cosmos ranked higher than Terror.
Using the LFR versions.
Essence of Terror
Haste: 6121 for 20 seconds, 105 second cooldown, 15% chance. 1166 haste on average
Light of the Cosmos
Int: 2866 for 20 seconds, 45 second cooldown, 15% chance. 1273 int on average
The primary issue with the cooldowns is that since Cosmos is a dot proc, while Terror is a hit proc, Cosmos is less likely to proc. We can therefore adjust the cooldowns to 110 & 55 seconds.
Terror: 1021 Int, 1113 Haste
Essence: 1041 int, 956 Haste
Difference (Terror - Essence): -20 Int, 157 haste
The difference gives 7.85 haste for every 1 Int, and there's no way that Int is ever going to be worth that many multiples of haste. Therefore Terror is better and we don't even have to look at the stat weights (which, incidentally, are incorrect).