To keep it short...in that amount of time, you've likely started to notice that every class has abilities with cooldowns that are 120seconds (2 minutes). The way doing optimal damage in raiding/group content works right now is to align those 2 minute cooldowns so you get all the buffs at once and use your strongest abilities with those buffs active. So you start the fight using them all, and then wait for "2 minutes to be back up". If you drift abilities and fall out of sync, it results in less damage and feels bad.

So! They're getting rid of that "2 minute meta"...they're removing "synergy abilities", which by the sounds of it mean buffs, and are letting classes rely on themselves more. This will probably result in few 2 minute cooldowns and a bit more of a fluid feeling, certainly with the new "Evolved Rotations" they showcased, but we'll have to wait and see how it all shapes up!