It's what leokimah said.
Basically, at FE, nowadays, most of the time, e-caller is just made to double rush a pre-cast and take down the opposite guild.
Your guild rush, you go in as last, stuff get bad but your guild is able to kill some of the important players of the opposite guild even if it cost you a big portion of your members, go out to pre-emp room, e-call and clean the leftovers to win+sinx sneak in to break to emp to get the castle.
Pretty much all the good guilds know all the tricks that can be used against them and against you and then is like impossible to e-call at the emp room because every smart guild have an hp or prof at the emp ready to sw it and also ready to Heaven's Driver or Thunderstorm(as a Prof) or holy light(as a High Priest) the stalker to stop the e-call.
Yes, you can swap gears and stuff and get miss here and there and you can use devo too but there is more then just one way to stop an e-call. Things as marine sphere Accessory does exist, Stapo cards too, champs doing Body Relocation non-stop at the emp room too, dispell for the devo too so hardly you can e-call by the sneaky/use the chaos made way like before in a emp room on any good guild because a good guild has eyes in every corner and have Boxs of Sunlight+Box of Gloom+Marine Sphere Accessory or a Maya Purple+Box of Gloom+Marine Sphere Accessory ready to use.
Basically, almost everything works nowadays to e-call at a FE.