Linen is possible but extremely slow for WVR's in their 40's. I have made it to 44 by doing this but even with massive HQ boosts, I can now only get about 2000xp from a single linen recipe. The problem you run into with grinding like that is the shard usage. At full speed in harvesting Lightning Shards in Thanalan since I can only use the boost once every 5-7 minutes I can only average about 3-4k shards in 6 hours. This game was designed to be more about the questing and content than the grind and this is a boring grind.