As far as I know most mobs have low magic resist. And there are very few that actualy are immun to magic.
Comparing it to other elements, the killspeed you gain from - res as a magic build is way less effective.
On fire/light/Cold/poison builds you meet a lot of immune mobs and with a sunder, your killspeed on them and overall clear is increased a lot by going for - enemy res stats.
But since there are almost no immunes and few mobs with high magic res , your damage increase from - magic res is much less effective than it is on other elements. Like if you are a fire build and every third mob is immune to your element you will gain much more out of a sunder and stacked - res. On magic that’s just not the case.
Afaik it doesn’t even do anything on FOH. Since FOH ignores the magic resistance from the mobs it can hit , - res doesn’t do anything .
But even for hammer the stat is way weaker than many think cause of the reasons I stated above. It’s not bad , but I would not focus that hard on it while ignoring stuff like + skills. Magic damage % is definitly stronger in most cases
Definitly should go for 1x sling max , opalvein or Soj second. Also should use a sunder with dmg %.
I kinda like gheed belt but on Helm a 3/20/2 should be better.
Using a pride merc for conc on hybrid sounds super cool though !!!