Lv50 creature in lower level area?

[Erudain]

Even if you can solo the B-rank (the non-aggresive ones) you'll get nothing....maybe some exp (they give exp to Chocos).
You can't get the money and seal reward unless you have the hunting bill for said mob.

A-ranks and S-ranks cannot be soloed, you'll need several ppl helping.

[Alukah]

http://ffxiv.gamerescape.com/wiki/The_Hunt

Don't try to solo A ranks or S ranks, B ranks are worthless unless you get the weekly bill from your GC (once you hit 50), when A or S rank spawns you will most likely see a flood of shouts of people asking for invite, the best way to get full rewards from those monsters is by partying up with other people.

[Enkidoh]

http://ffxiv.gamerescape.com/wiki/The_Hunt

Don't try to solo A ranks or S ranks, B ranks are worthless unless you get the weekly bill from your GC (once you hit 50), when A or S rank spawns you will most likely see a flood of shouts of people asking for invite, the best way to get full rewards from those monsters is by partying up with other people.

They're not entirely worthless, as they still count towards the Hunt achievements regardless if you have the Hunt Bill or not, so if you're after the quest titles from them it's still worth doing. Or if you're bored and are feeling particularly bloodthirsty (I like to hunt B rank NMs for sport myself even if I don't have the Hunt Bill for them).

[Teslo]

Heh. This reminds me a story I had a week or two ago.

Was playing FFXI and had to complete a mission for my lvl 50 BLM. I had to go through Ranguemont Pass which had a bunch of lvl 90's dumped in it according to my friend since Abyssea dropped (for leveling)... great, well sneak + prism powder did well for that. Finally get to Fei'yin and slowly battle my way to the location I need to be. One room before I can get to the thing I had to activate, I find a NM. I ask my FC mate on mumble if he heard of it... nope. I look online, lvl 80 NM... ooooooh no. It then moves up to me, aggros, and one shots me as I run for dear life. Had a laugh and tried an alternate route after getting back.

This is a fairly common story from FFXI. Most people I've met have a similar tale. lol

They loved putting quests in zones that were WAY higher level than you were when you got the quests...