Green and blues are garbage, stuff you trash and sell/shard without even looking at it. Yellows are 99% of the times shardable and 1 of the times material for the TP.
Champion bags give loot with the same frequency than anything else, aka total fucking random close to 0,0001% of getting exotics. I have 5 level 80s, clocked a ton of hours on them at level cap, doing trains, world bosses, dungeons and all I got was ONE single lame shitty exotic piece of gear (I WAS around +100% chance magic find, since they changed the way that works).
As much as I loved GW2 world, loot in the game is pretty much insignificant and unexistant. It was purchasable, tokens and laurels, which meant daily ruuns and daily/monthly quests. Did it for a while, then got bored.
Not sure if trains are still going, which were a stupid thing by itself, but either I was the unluckiest player ever, or they ain't worth doing (and absolutely not fun at all).