Priceykins is right, witmans has a decent drop rate (at least for me). I used to farm there all of the time to make some easy money, and I also found my now customized req 8 15%^50 Felly. Even came with a 20/20 on it

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I also enjoy going to Thunderhead Keep. The Mursaat are a little more tricky, and if you get caught by a mob of ice imps it really slows the run down. Good Mursaat drops there. Sold a req 8 15%^50 Mursaat bow that I found on a run with my buddy for 100k+75 ecto.
That was the old days though.... I find that the drop rates are crappy if you chest farm too much. I like to do a quest, a mish and farm with a group for a while and it seems to reset the drop rate a bit.