It may not be a developers job to make smart players, but they can certainly encourage smart play (or “incentivize” if you’re into the whole corporate buzzwords thing)
Why not have advanced mode actually be advanced? Throw in a few more tricks for the bosses (please don’t just make them bullet sponges though). Require communication and dedication, with the understanding that even the best players with all the skills and communication in the world might fail. In fact, you’re almost certain to fail the first try or two.
Quick example, using a boss we’ve certainly all fought : Varelsi Conservator. Add extra Shielder units (whatever they’re called) and have only 1 vulnerable at a time. For extra difficulty, any damage done to players by the death bubble could heal the boss. You could add another trip to the “Space Dimension,” and if you wanted to get really nasty, add a minor health drain that ramps up the longer you’re in there (and maybe that heals the boss, too)
Now you have a genuinely advanced fight. One that requires teamwork and planning. One that will probably require a slower approach to the rest of the mission, to ensure everyone is level 10 before they fight that joker. And when you beat him (her?) you’ll have earned the greater rewards.
Edit: maybe make this advanced advanced. Super advanced. Maybe even just 1 or 2 dedicated PvE missions that explicitly say “designed for a group. Solo this at your peril”