When using PE just treat your FET as you normally would, have it go attack, you can ignore the buff it provides as it's a dps loss for it to not be attacking, it's a really lackluster talent in my opinion as it just adds more damage done by your FET, nothing else really. PE has become typically the stronger talent choice due to haste stacking in ToT since pets benefit most from haste and agility from us.
Just to also catch you up, haste is becoming the preferred stat to push towards because of the legendary meta and all the RPPM trinkets and how they synergize better with haste as a primary stat.
As for using PE for AoE packs and the like, that's more likely going to be a waste of the PET to not use it properly during a burn phase or an instance where you gain a dps boost, if you're looking to push more AoE out taking EotE would be a better bet. And PET has a long cooldown for a reason, it's a large dps CD, you can't compare two talents in a tier and say "well this is better because I can use it all the time vs this long CD" they are balanced like that for a reason, one provides more consistent dps and the other provides amazing good burst dps - PET glyphed + Ascendance gives you amazing burst every 3min.