I recently started playing Diablo 3 again, so I'm not much into the whole "what's best to do". On leaderboards, there's a trend to go for defensive attributes over skill modifiers. For instance, a standard marauder build, people choose all-res or life % over sentry % or cluster arrow % increase. Why is that? It seems like a lot of damage to miss.
It depends on the build. Sentry % is not a good option if you use Hellcat Waistguard, most of your damage comes from the grenades, but there's some bug that the belt's bonus doesn't work on sentry grenades. Wudijo certainly knows more about this. Cluster Arrow makes sense though, and he also recommends it on boots, but not on helmet (I guess because up to 1000 vitality are just too good to give up).
It just depends on the build, where your main damage comes from, and if skill damage affects it. For example, if you play a generator build, obviously the only damage skills that matter are those on belt+pants. If you play a Manald Heal wizard, there is no skill damage for that. People are not "avoiding" skill modifiers, they're just not using them when they're not useful, which is sometimes the case. Also, sometimes you just don't get that gg rolled piece of gear, and getting the right skill on a quiver is a pain in the ass because there's like a million different affixes that can roll (and CHC and so on are way more important than skill damage).