I'm not sure there IS another way to rule the Krogan besides fear and intimidation. Remember, every Krogan has the Blood Rage gene (Before they nuked themselves, they would lock up Krogan with that mutation as a danger to society, their right of passage involves getting your friends together and killing monsters. For the last couple thousand years they've been living under the collective assumption that they're a doomed race with nothing left to lose. Maybe one day, after their society stabilizes, you can have Krogan leaders who don't rule through fear, but right now their culture is such that nothing else works.
Remember the Shaman in ME2, Shepard's headbutt doesn't just shut up the other Krogan, it Impresses the Shaman. Ruling through Fear is not just a way to cow your enemies, it also impresses your supporters.

The difference between Wrex and Wreave is that Wrex recognizes that Power is a tool, not an end. He knows that Krogan Rebellion II: Biotic Boogaloo won't turn out any better than the first one, and that the key to the Krogan's future is proving to the rest of the galaxy that they can be something besides thugs.