Originally Posted by
Azerate
The idea that high level players will want to farm low level keys en-masse because of the valor upgrade makes sense at first, but if you really think about it and consider how the system works, it turns out it's not so good.
First of all, in order for valor to actually matter, you need to get the actual items first. And the higher the original ilvl of the item the less valor you need. So people will naturally attempt to get these items from +14 and 15s instead of low level dungeons. Secondly, you still have the great vault, which is the core of m+ gearing because it gives you 226 options weekly, and you need 10 dungeons done at the highest tier for 3 226 options. So you will still want to prioritize that over anything else.
In other words, the only time when it actually makes sense to spam 2s and 3s is when you already have the item you want to upgrade from a +14/15 AND when you are already done with your 10 weekly dungeons. An average player will probably not do more than 10 dungeons per week at all, let alone grind low level keys ad infinitum after doing the weekly cap of 10s.