There are functions in some daws (I can only speak for Mixcraft in particular, since that's my primary daw of choice) where it can determine the key of a given song - not full proof with songs that change key, but it's a start in the right direction. From there, determining pitch shouldn't be too difficult with a guide for what pitches are in that key (you'll need to know a bit of music theory, but learning the treble clef isn't hard).
Another way to make midis easier may be to utilize a voice - your own, alterego, aquestone, vocaloid, etc. Or use an instrument that's distinct (a plucked or percussion one might be best, all depends on the person).
That all said, I don't mind making midis, but my problem right now is a lack of voices for each situation - Vocaloid wise: Japanese female (soprano, alto), male (tenor/countertenor, bass), Korean male (tenor and bass), female (alto), English female (soprano, alto) male (tenor, bass - Oliver is treble). Sure, any voice can theoretically do a song meant for another part, but the point is, no one voice can do everything.