Kevlar is a newbie mod by design. No advanced player would sacrefice speed over health. Meanwhile for newbies with bad positioning it can solve at least a tiny gap of the huge skill gap to get at least one or two kills. It's not designed to be competetive. Also any changes that would make it viable for good players will automatically make it overpowered compared to Clothing Agent, which has a huge negative stat if you haven't observed that.