Why doesn't pve have pvp combo structure?

[ItMe]

Since no one has answered this question (it's almost like people are avoiding it) I'll ask you. Why is pressing 123 more complex than 111?

I don't think it's a question of the gameplay being more complex with 123, I think it's a question of "how do you make DNC or DRG into 111?" And that trying to make them 111 would be no good because most non-tanks have combo trees and aren't even 123 to begin with.
Also, the first response on this thread is about how there are times you DON'T wanna push 123.

"when you're never gonna break combo anyway"

I've had to break my combo early in TEA so I could use Goring Blade on Brute Justice as soon as he spawned, saving me 2 GCDs and allowing me to go immediately into my spell rotation to hit BJ and CC then reapply Goring Blade before using Passage of Arms on the 9th-12th J Waves.