My god this sounds exactly like academia: your job as a professor at a research university is to obtain grants, publications, and donations. Pretty much everything else is incidental. "Service" to a department, to students, etc. is "emphasized" in reviews, but if push comes to shove, the asshole with a bunch of big grants is going to steamroll the "nice" junior faculty who "mentors" the asshole's students. If you're teaching, preparing to teach, or holding office hours, you're not writing grants or manuscripts. And the odds are that everyone will say "thank you so much!!" as you get turned down for tenure, UNLESS you managed to satisfy your true primary responsibilities so efficiently as to leave time for the "fun" stuff (teaching, watching people discover, blah blah)

There's a balance -- you can do more with more hands, and they need to be well trained hands. But if they're not your direct reports, ultimately they're not your problem. (This also means that you will need to be responsible for the outcomes of those you mentor, and you'll need to learn how to let slow learners go. Oh noes, you're becoming management! It's almost as if there's a reason that good managers with domain expertise are hard to find.)

I guess it comes down to, are you going to be a "helpful" "mentor" or are you going to accept formal responsibility for the success or failure of mentees (vis-a-vis grants, contracts, successful projects, etc.)? Instead of being a martyr, it seems that explicitly accepting or denying responsibility for people who eat up your time (within reason) is the best long-term strategy. You can still succeed without doing this, and you can still fail while doing this, but the odds are in your favor if you demand accountability. (Also, there's nowhere to hide if you aren't as good as you think you are; I think that's a feature, rather than a bug, but opinions may vary.)