Yet people are playing at 60fps at 1080p on a gtx 970 just fine on ultra.
I mean I could see needing the 6gb if you were going 4k but 1080p I'm not seeing it.
Well worst comes to worse I guess I still have another week to return. *shrug*
Some have complained about experiencing minor stuttering despite high fps because there is hitching when the VRAM reaches limit.
Also if you want to max out this game, you have to increase resolution setting above your native display to enable SSAA. It's rendering at 150% or 200% of your display and downsampling, that's what Mordor uses for anti aliasing.
Unless you want to run the game without anti-aliasing or force a different type from your graphics driver menu, 1080p display needs to render at 1440p, 3k or 4k in order to enable SSAA. I'm guessing there will be more upcoming games that make use of use DSR/supersampling this way, Witcher 3 most likely.
Most of that is preloaded and leftover data that's unnecessary. Allocation exists. If a videogame truly uses more than 2.5 GB VRAM at any given point, it's a telltale for horrible optimization and most likely memory leak.
VRAM amount is mostly just a big number for manufacturers to fool people into buying higher VRAM SKUs at a higher price. Decently optimized games up until WQHD resolutions do not require more than 2 GB VRAM, anything more is either reserved for extreme resolutions (surround vision/4K), or simply developers having coded a mess.
That certainly used to be the case, but it's not just a marketing tactic anymore. There are a few games actually making use of higher amounts than we used to see a few years back. Looking down the road I imagine we will see more titles like this. DOOM 4 and Witcher 3 probably going to be among them.
For example, you cannot even activate the highest settings for Wolfenstein New Order unless you have at least 3GB VRAM. I have no idea about the optimization for Shadows of Mordor or Watchdogs, but Wolfenstein New Order is very well optimized. It makes efficient use of both CPU and GPU. It eats VRAM however, for best performance as texture data streams from your SSD, system memory and VRAM.