Any time that valor capping is optimal for raiders even when clearing the current raid content, the trivial content that awards valor is going to have people doing it that vastly outgear it. Either the intro content needs to be more difficult and raid content scale less (raid gear not be as much better as now) or trivial content shouldn't be required for valor or people will have to do trivial content as a chore for valor and not like it because it is so trivial.
Scenarios, heroic scenarios, and challenge modes don't award trash drops. Dungeons used to be a non-trivial source of enchanting materials and cloth. It just feels bad to run content that doesn't have any rewards other than valor.
A group of us started doing challenge modes for the 3 per week complete for 1500g for raiding repairs. We are 5/9 gold doing one each week. It just feels wrong to go through and stomp the place up with a "go, go, go" mentality and not get anything physical out of it. Mobs have loot and gold. I want them. Competing for "realm best time" or "twinking challenge modes" with just the right classes and the gear with the most gem slots really doesn't interest us. (We also don't twink low level pvp.) Challenge mode gold is "memorize this optimized pull strategy and bring your invisibility potion". Clear the trash right (and have enough stuns) and you get gold.