Gold should be based on time not which activities you choose. All activities should provide similar gold rewards for time invested. And as far as PvE is concerned most are somewhat close. There doesn't seem any real reason to make one activity not rewarding compared to the others. Let's be honest the vast majority of PvE activities are not difficult in the slightest and you should not be dieing AT ALL, the only time you die in PvE is doing progression raids, and in bad LFR groups. That is still a tiny slice of the gold generating PvE activities people participate in and even in bad LFR groups the gold provided with quest rewards covers repairs, and I am still getting gear, fail bags with gold and gold and gear drops from trash.