For those that think the shield duration nerfs are "too harsh"...
Just remember that teamfights used to last more than 10 seconds and that you couldn't have shields at >100% uptime, so a 6 second shield duration makes sense. Because of a much larger downtime, timing shields mattered and was one of the main sources of skill expression on enchanters.
Now that teamfights are getting shorter and shorter, shield durations will have to be as well. A 6 second shield in teamfights that last as long as shield durations basically threw one of their main sources of skill expressions out of the window, therefore making them "much easier" to play because of less downtime, plus the overabundance of CDR.
In other words, it's basically an "update" to the length of teamfights. Sorry, you can't just autobind shields to your allies 24/7 anymore.
Also for those that are wondering, Pix will still stay for the full 6 seconds when tagged with an ally, unless someone else have played Lulu on PBE and have proved otherwise.
EDIT: After reading a lot of comments, yes, we know "faster teamfights" stemmed from the overabundance of damage. We also know how Riot balance team works, they don't just simply "undo" things. But opening up windows of skill expression is most likely going to be their reasoning behind the shield nerfs, whether you like it or not.
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rework uses are literally making up 70% of the active popular champ roster right now, and generally offer little to know counterplay.