The Act 5 frenzy barb will out DPS any other mercenary hands down. But, if you are looking at these guys for overall DPS, then you are wasting a lot of resources.

Then equipping an Act 3 merc with gear as many sockets of possible will still work. The old strategy of selling your first born child and left nut for a slew of rainbow facets. So, let’s get the obvious point out of the way. Hopefully, this will help some players decide if they want to give them another look and put all the options on the table. There are some edge cases where they are the best overall choice for a particlar setup. This write up is about how to best leverage and equip them and where they fit in the mix.

That being said, I don’t see them ever being the mainstream option. I have been working a few of them into my builds lately and they work a lot better than people seem to be giving them credit. The Act 3 mercs are universally thought of as nicely improved but, still not good enough to consider using. With the recent 2.4 mercenary rework there has been a lot of discussion about what the new best merc is.

Diablo 2 mercenary guide