I've noticed this twice on the forums, in General and in Raids & Dungeons. A request that 10-man loot be equivalent to 25-man loot.
First you have to go on the premise 10-mans are as difficult as 25-man dungeons. I cannot speak from personal experience, but from what I've read 10-man Sartharion + 3 drakes is harder that its 25-man counterpart. One encounter isn't enough to support giving a 10-man boss the same loot table as a 25.
Just as Blizzard decided to decrease from 40 to 25. The argument is more people cause more complexity. And this I agree. How often have you beat an encounter because of less people than more. It happens. The oft quoted "herding more cats" is mentioned when discussing why larger raids are harder. It's quoted because it's true.
Also don't forget, if there is a instance tuned for 5 or 10 you start to have to make it workable for a variety of specs. You end up having to water it down so Joe 'n Friends can down it with whatever class mix they decide to have. If they tuned it tightly to make it rough going, many of these close knit group of friends simply would not have the necessary elements needed.
What I found most interesting is a few people saying they should just get rid of 25-mans altogether. But they didn't really give a reason why. To me it sounds like some players want their 10-man achievement to be the pinnacle of the game. Which makes them no better than the elitists they despise.
What happened to smaller groups just want to see content?
It quickly goes back to why do you need 25-man loot if you are only willing and/or able to tackle 10-man instances? I remember when I had decided to take things more casual I knew I wouldn't be able to have access to the best loot anymore. It seemed fair to me.
Time is not of the essence
2 hours ago