If Comeatmebro's explanation is correct (and it makes a lot of sense to me) then in theory you could be able to replicate this even with GS/Ashita, simply creating custom rules that avoid the usage of Precast/Midcast/Aftercast logic but simply execute actions in a sequence with fixed /waits in between.
That's more or less the approach I'm taking in my new attempt. Well, my approach really only goes halfway.
Precast & midcast should always be reliable, because they don't rely on server messages. So my plan is for blood pacts to use midcast to equip BP timer gear, as well as start a 200ms timer to equip your BP gear that would normally be equipped on pet_midcast.
Do gear sets get affected by this issue? First time in Dynamis lastnight as summoner and my BP timers were all over the place from 35s to 21s and damage was crazy affected.
I would imagine they would be impacted as well if it's communication between client and server..
They shouldn't be, if you're using Gearswap. If using in-game macros, it may be possible. That said, I do sometimes have this happen to me but it's extremely rare, like once a month at most and have never had it happen twice in the same event.