I believe developers should decide right up front whether to go PvP or PvE, and then whether to choose a loot based or crafting based economy. Trying to be all things to all players just makes everyone miserable, or at least that's how it's been in my experience.
Balancing combat for PvP ALWAYS fucks up the PvE gameplay, and you can never please PvP players anyway because someone always loses and those people will want buffs/nurfs constantly. The two play styles just aren't compatible, because in PvE the player should feel powerful and unique with class specific abilities and sometimes unbalanced class strengths/weaknesses. Conversely, in PvP everyone needs to be relatively even and balanced, with homogenized classes so that everyone feels equal.
Economy is very similar in that PvE players want to adventure and discover rare items as loot, whereas crafters need everyone to buy their wares in order to justify and financially support their play style. PvE players despise item decay, and rightly so since maintaining looted items until they disappear is a miserable experience, and it goes against the classic fantasy idea of ancient artifacts like Gandalf's sword Glamdring which was far better than could be made in modern times. Oh and Glamdring was even looted from the Troll hoarde too. Crafters on the other hand require item decay in order to maintain continuing gameplay with return customers/item maintenance. Loot can't be better than what they make and nothing can last forever or they'd be out of a job.
Developers should decide which way to go and then stick to their guns, because in my experience you just can't please everyone. Wow, that was really long winded. Sorry.