My opinion is that you do not need to take part in most hyped projects, because there will be too many participants and your total payments for bounty will be too low, better choose medium projects with no more then 200 people participating,more chance to earn some money
I quite agree with you, its a common problem of all bounties - when the number of participants increases, stakes and incomes decrease. That is why the biggest profit you can get from an unknown project - because it has the minimum number of participants! (And working idea and team, of course).
Also the question "How to pick best signature campaign" is similar to another, that you often can read on the forum - "How to find good /profitable/perspective etc. bounty". Its a complex question and needs only your own thorough analyse.