"I'm confused" is much better than "I may be wrong" and (especially) "I may be biased". It's just as modest, but more informative.

And -- importantly -- it links the modesty to your epistemic state, not your seniority level. To the extent that "I may be wrong" is, as you say, a truism, it doesn't communicate any information about your knowledge and is just verbal filler whose actual meaning is unconnected to its semantic content .

On the other hand, examples like "I may be biased, but my relative Person X is the greatest person in the world" are clearly instances of undermining one's own credibility. As such, I find them grating.