I've grown many times without any type of humidity dome, if it is giving you that much of a problem maybe try popping them in a wet paper towel and planting them when the tap root comes out, then just let them grow without adding a humidity dome.
I personally think a dome is more important for clones than for seeds, but I have done both without using a dome. Never had a problem sprouting without a dome, only reason I use one now is because I have one, but for the first 3-4 years I grew I never used one and never had a problem...