Many of these questions would now be better placed here than on the site they were originally posted on. Should we actively seek out migration of good, relevant questions from other SE communities which would fit better here?
First of all, we can't migrate questions older than 60 days. Moreover, the general rule across all SE sites is that we don't migrate away things that are on topic. So assuming the questions were indeed on topic where they were asked, there is no reason to migrate them.
Instead, what we should do is when we find an interesting bioinformatics question on another site, we just ask it again here. We can either use the existing answers from the other site directly (with attribution, of course, and possibly marking as Community Wiki as well), or write our own.
But no, migration of existing questions isn't the way to go and isn't possible anyway.
Although some questions about bioinformatics might be answered in other Stack Exchange sites if they are on topic on that sites it doesn't need to be moved here unless the OP asks to move his/her question.
For example some questions are on topic both in Stack Overflow and Software Engineering, but unless the user asks the question is left where it has been asked.
If it is a borderline question, let it live in both cultures, as the answeres will be different, programmers answering for programmers, and admins answering for admins.