Honestly removing Rouse at this point would be better. It's the hardest skill to fit in cleanly amongst all the other lockouts. It doesn't work with Bahamut, and therefore has to be used after spending Aetherflow but ideally before/during DWT, making it hard to line up in the opener and likely to collide with Bahamut if not properly managed, and on top of all that it offers the least dps gain. 40% is a lot but it's on your pet, which deals around 25% less damage than you would, while having weaker skills to burst with during that time, aside from Enkindle (Not guaranteed to line up thanks to the proc).

I wouldn't be opposed to giving back Sustain as a cooldown in it's stead with the %HP Regen and Rouse's CC immunity effect. Ideally this would come with a fairy buff to even it out (slight potency boost to Fey Union and maybe Embrace), but that's cause SCH has it rough too.