what is the max lvl i can be to farm lvl 50 monsters without a drop rate penalty?
After you are 4 levels higher than a mob, drop rate becomes crappy.
But pretty much all level 50-60 BAMs have horrid drop rates to begin with. So don't bother with BAMs a few levels lower than you unless you can easily take it down within a few mins.
Level 30 BAMs drop better than level 60 BAMs for a lv 60 player. It's ridiculous.
The higher level the harder it should get... it should be like that!
Another reason to be looking forward to Guild Wars 2 and a strike against Tera, in my opinion.
In GW2 you can't out-level content. So, if you're level 30 and dropping by a level 10 area you never had the opportunity to visit, your power is temporarily scaled down to that of a level 10 character. This way you match the difficulty of the area.
That means every area will always be challenging. Every area can be viable end-game content. And since every area will always be challenging, risk versus reward remains intact regardless of your true level. And because of that, those level 10 mobs will be dropping loot appropriate for your true level (30, in this example).
A much more beautiful way to handle it, I feel. Tera simply penalizes the player for out-leveling content with one hand while throwing XP at them with the other. (sigh)