Voidwatch is actually limited aswell, you know. You need a voidstone to be eligible for any rewards. If you spam voidwatch, you'll run out of voidstones pretty quickly. Then you need to either a) spend IS, AN or CP for voiddust, or b) buy voiddust. Eventually you will run out of IS, AN and CP, forcing you to do campaign battle as the most efficient way to be able to obtain more voiddust. Or you can spend a shitton of gil buying it. Voiddust is currently selling for 20-25k each on my server, that means ~100k per run.
Either way - with the voidwatch system being as it is, there is a lot of grinding involved. Changing it to be more like Einherjar also means grinding, but my point is that at least you know you will indeed get that piece of armour in the end. I don't know about you, but I prefer my grinding to actually yield a reward in the end (reward as in something I actually want, not logs and ores). Instead, now you can spam voidwatch week after week and get nothing to show for your efforts.
By the way - you said 3 fights and 6 loot pools - that means you have 2 characters, and you say you averaged 2-3 plates per round. And you weren't talking about pouches. To the best of my knowledge you can only get 1 single plate per fight per character, at least I have never heard of anybody getting more.