Aside from various subjective opinions regarding achievements/trophies the reality is these should work like every other game on the market or not be included.
Whether you like it or not trophies/achievements are included with games for a reason. They are popular and help build player attachment and retention. For many players they add value to a title which in turn is good for devs and publishers.
I have NEVER played an online co-op game on Xbox 360, PS3, or PS4 that only allowed one player to earn achievements. These titles might exist out there but even with my prolific gaming history I haven't seen one.
Making these work correctly may not seem like a big deal to some, but to others it is as important as making sure your characters skills work correctly.
Achievements/trophies should either work correctly or not be included.
Personally I would prefer if games just gave you a single medal/gold star/trophy/virtual cookie whatever for completing the game and left all the other grindy achievements out of the mix but my idea would be wildly unpopular for most players.
Just because I really don't think trophies/achievements are all that cool does not mean I can't see why they are for many gamers.
