The first one is still wrong. "Underestimate the technical feasibility" means, "They think it is less feasible (harder) than it actually is." I think you mean the opposite: they think it is easier than it actually is. I.e. you're trying to say it's harder than we think.
You can say instead: "underestimates the difficulty" or "overestimates the feasibility."
James, you are correct but I think JunkDNA's point is still being made effectively. In fact this was likely an intentional statement meant to illustrate the difficulty involved in intentionally creating a thing--if an error could be easily introduced in a handful of words, how likely is it that a malicious DNA creator will get their supervirus working exactly right?
That is very optimistic of you. Personally I think it was more likely that it was simply a typing error, as he has acknowledged. That's fine, we all make them. I had some difficulty parsing what he was trying to say, which is the only reason I brought it up.
The rest of your argument is very far fetched. One person's difficulty formulating a sentence could not be less related to biologists' collective capabilities in tailoring viruses.
You can say instead: "underestimates the difficulty" or "overestimates the feasibility."