Best damage bonus to have?

Hi. Just trying to simplify things after reading some detailed info on how damage is calculated. So I know if I should start seeking a bonus I’m currently ignoring or not taking seriously enough.

I know some damage is added, and some is multiplied. But some of the multiplying bonuses don’t seem to be that big anyway, and that confuses me further.

Lvl 70. Been in Tier 4 as early as lvl 63, and it was tough but not impossible. Tier 3 has usually been quite easy, for a long while now.

My main attacks are Lunging Strike, Death Blow and Upheaval. Ultimate is Iron Maelstrom. Finally, I use Leap and Steel Grasp.

I know it may sound wrong with how popular it s, but I avoid relying heavily on Critical+Vulnerable damage bonuses. I’d need to change much of my build, to get a decent chance to even trigger Critical (Vulnerable, I trigger often enough). So, please don’t suggest that combo.
Overpower is similar, right? Nice in theory, but hard to trigger.
All this of course, unless you can suggest a way to give crit or overpower a large chance to happen without needing to change half my gear or so.

Thanks for your time.

Well even if you want to avoid Crit and Vulnerable, you will have to incorporate them eventually for end game.
I play barb too, got 40% crit chance with 400% crit damage and 250% vulnerable and I cruise thru Tier 100 dungeons.