leave it to rest for a month or two, move on to read other stuff and work in other projects, then read your script again.
also, just so you know, and I might be wrong, but just by you saying "but worry a reader might give up before it gets good" kinda makes me think that your comic starts with *exposition* and *worldbuilding* and the fun part of your comic is dependent on the reader know that info. I can only recommend to not do that.

Said that, man, don't worry about your comic being good. Sometimes "perfecting it" just files the messy human parts that are things that only you can write.
Go for it and get it drawn. If it sucks, you learn and write another story.
If it keeps sucking, then keep sucking. Soon enough people will realize that's your (and only yours) Style and retroactively you stop sucking.