Investor is not feeling worth it in my first test.
+1% Skill Efficiency = +1% Skill: Haste-Duration-Damage-Heath-Status Effects-Repair Skills
Build:
- 3x Empress International pieces, 8% Skill Efficiency.
- Investor mask with 3 yellow skill attributes, 15% Skill Efficiency.
- 2x Ortiz Reficere pieces, 8% Skill Efficiency.
- 31% Skill Efficiency and build around this.
Other ideas is with the Perfect Investor you could actually just run this alone on any other build and have a nice hybrid. You could run lower tier skills and have excellent performance.
Note it took me over 100+ reconfigures of the Investor exotic mask to get this roll. In fact I had to put it in the stash so I would stop seeing it and wasting exotic components on it, addicted to rerolling it. My original dream roll was for an all blue Investor +3% armor regen but this roll happened, will get another Investor and reroll for that next.

Tried a first build with explosive skills shown in photo above 31% skill efficiency, did good but seekers were still around 4-5 million per hit which I already get using china piece on other build. Sticky explosive was hitting for 10 million at times, need Anomaly augment to heal because these big booms generate lots of threat. So this build is not anywhere near optimized but a nice first test. I feel like this is underperforming, my seeker cooldown is around 30 seconds with no haste mods, maybe Investor is not working? Need to math it out.