Entropy is not a problem, surely! The choice to return deterministic values for random() is a feature, not a bug. When you are crawling pages, looking for meaningful content changes and new links you probably don't want your random() creating noise.
More than enough. Chromium takes only 128 bits from /dev/urandom to seed a V8 isolate. You can also use a fixed seed like Googlebot by passing the command line flag