If you're doing progression still, you should be using all your VP for the maximum possible performance gain that week. It seems like the people that aren't seeing improvement just aren't using their upgrades. If you happen to get a BiS item, you probably shouldn't upgrade it right away; compare its value of going 0/4 > 4/4 vs going 2/4 > 4/4 on two of your existing items. It's unlikely the 0/4 will come out ahead unless you only have rings/bracers/necks left at 2/4 and just got a new weapon/trinket.
If you were vigilant in capping VP and came into the patch at 3k and upgraded gear for the highest performance that week, you should have an extra 5 ilvls by now. That's an extra 5-8% DPS/HPS/Survivability across your raid. There's no way that hasn't helped progression. You may not have killed a new boss yet, but you should have gotten closer.
If you're already 14/14H and getting bored, sure, just use your VP "efficiently" (upgrade BiS items, then pool 3k before upgrading items with the potential to be replaced). This is highly ineffective for increasing your performance week-to-week, though. It will only save you time VP capping by the end of your BiS gearing (which could take months or just never happen anyways).