Ending up in Toto-rak/Tam-tara for the 1,000,000,000th time wouldn't be so bad if I could at least do more than spam one hotkey. I can't think of a decent reason why we can't have scaled down potencies on all our skills in level synced content.

"But that content wasn't tuned with those skills in mind"

I don't think level synced players care about how old content is tuned.

"But a newb might see all those flashy skills and be overwhelmed/jealous"

A newb will think "I can't wait to do those flashy skills myself!", and be more likely to invest time (read: sub-money) into leveling his character.

I can, however, think of immediate benefits to this.

-High level players more willing to queue for low level content, keeping queues lower for newbs.
-Not having to constantly switch out spells that get replaced (Stone III, Malefic II, etc)
-Not having to remember what was a good rotation at level xx
-Players constantly practicing their current rotation/skillset in ALL content will improve the playerbase.
-Shield Oath.