To start with, it is hard to rank top 3 overall because most eddies are specialists (which is a good thing imo)
1 - I believe max awakened Cyborg wins this, he is effective everywhere.
2 - Then we have a specialist: LAD Eddie is the current arena specialist and very effective.
3 - I would place Van Helsing at third place, great passive + damage + survival skills.
I haven't tested the Thor Eddie yet.
About the farmers, Navigator is a nostalgic one and still can be reliable.
But if you use Blight set on any eddie with AOE basic, you can turn them into a speed farming machine (saving time from using power & fury animations)
Currently I run Beast Eddie with Blight & Shadows, along with an ally having eternal or yggdrasil set (to activate shadows) and it is blazing fast.