You can't just look at the changes and say X is top and there's no debate. It matters based on the fight, based on your playstyle, and most importantly where you are at in gearing (aka your total stats). As you gear up through ToT you'll be able to push a lot more haste out of your gear, which then favors EM/AS+PE more than a mastery based build of EotE+UF. However there could still be fights where specific talent choices are just more efficient, and I personally prefer using AS+UF as my default go to DPS build for most fights as I prefer to consistent dps I'm able to put out with it.
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.
Similar to what I just wrote in response to the previous quote, the difference between UF and PE should come down to what the fight demands, your playstyle, and what stats you currently have on your gear. Typically on fights with high and predictable burst phases (i.e. Jin'Rokh) PE is the better choice, especially if you have a haste focused build. UF is better used on fights where you need more consistent dps and when you have a more mastery focused build. I still stick with UF over PE for personal preference (do use PE on Jin'Rokh though, too good to not use).
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.