Couple of nitpicks:
1. In Cataclysm, after your seven weekly dungeons were done, you got zero valor from them, not reduced valor. They also didn't get you all the way to the valor cap IIRC. The Mists system of giving you 2x rep for the first dungeon or scenario is intended to split the difference, giving people options while discouraging repetition, but a 50% penalty seems to be severe enough that many players think of dungeons for valor as a daily thing.
2. You could get a small amount of Shado-Pan Assault rep each week by doing Champions of the Thunder King. It would be pretty slow, but I bet you could have gotten to honored, maybe revered before 5.4 if you did it every week.
I've been gearing a non-raiding alt on the Timeless Isle, just by doing the daily and killing Evermaw and the Boat whenever they come up. The pace of breadcrumbs from 496 to 535 is actually pretty good, giving me maybe two burdens a week. I don't even do LFR with this alt; I tell myself I'm gearing him up so he can kill and skin things faster.
I'll go out on a limb and guess that if downscaled dungeons come out in 5.5, they will come in two different difficulties, rewarding 516 gear from the easier difficulty and 535 gear from the harder one (which won't have a solo LFD queue). In the next expansion, they might come in three different difficulties introduced in odd-numbered patches over the course of the expansion.