So the way it is calculated out and the way a lot of damage “ticks” based on frames in D2 I think it is a lot more useful than it seems.
I would say if you can slot some into your build, great, but otherwise don’t obsess over it.
It’s really nice to get some amount of DR% from unique/set items but for SSF offline player that may or may not be feasible. The cap there is 50% btw.
Regarding purely melee zealot, I agree focusing on FoH or Hammers doesn’t make sense because of the reasons you said as well as the gear bonuses you’d want for Hammers is somewhat at odds with what you’d want for a zealot, and FoH is not terribly viable usually.
You will however need some way of dealing with Physical Immune enemies when you get to Hell difficulty.
Usually this is achieved by either breaking the physical immunity with curse/aura, using a skill that applies elemental damage like Vengeance, or from having high elemental damage on items/weapon switch. My focus is typically on barbs but I also enjoy zealots, it’s just been a while since I’ve taken one through Hell since mine in D2R is on hold while I work on other classes, so I don’t have a lot of great current advice for you there.