On average, Kilt provides 3% more DPS over GS, Cord, and Sephuz. Compare this to fire mages where Bracers/Belt provide ~7% increase over the next best legendaries.
Kilt is good, and makes conserve phase a breeze, but it's not objectively that much better than GS. It is definitely better than Armwraps IMO, which need their nerf reverted -- on top of the RNG of the clearcasting proc, it will often go wasted during AP phases, or expires when you have to move too much.