Believe it or not, countering bioweapons is incredibly easy. Until some of the bugs and exploits get fixed, it is possible to give them a hard time by utilizing the following methods.
Guide to Countering Bioweapons
Enter a Safe Room
What's more humiliating than not being able to fit through, or force open, a half-closed metal door as a 7 feet tall giant?
Being mocked by fragile mortals on the other side.
Just like in any other Resident Evil game, you are perfectly safe as long as you stay inside, but pay attention to the time.
Kick Them in the Butt
I main Tyrone for one reason and one reason only: being able to beat the Tyrant and G-Birkin at their own game. All it takes for these seemingly undestructible mutants to lose their balance is one simple kick by a 25 year old firefighter. In this game, feet are apparently stronger than bullets and grenades. You could use his personal ability to save your teammates (and/or yourself) from certain death, not to mention how useful it is against regular zombies too.
Lock Them Outside / Inside A Lift
Nobody can get in or out of a lift once it's been activated. You can easily use it as a secondary safe room by staying on the platform and activating it when the bioweapon gets close, or wait for the latter to get on the platform and pull the switch from outside. It works with bridges in the Abandoned Park as well. Make sure you get the timing right or you'll end up wrestling with the Undertaker in a small ring.
Stun Them with Flash Grenades
You should always keep one on yourself, they are extremely useful as they can incapacitate anything in their range for several seconds. Currently the best grenade in the game by far.
Tip: If the bioweapon is nearby/camping a defeated survivor, stunning them with a Flash Grenade will grant you enough time to rescue them before it can move again.
Blind Them with Martin's Flash Baton
Martin Sandwich has learned from other asymmetrical horror games that light is the biggest weakness of all monsters who are trying to kill you. It works exactly like a Flash Grenade, except that it's his Fever Skill and doesn't take up an inventory slot.
Run Around a Table
The oldest trick in the book, for which developers never really found a solution. From Dead by Daylight to Friday the 13th, running around wide objects has always been effective against big scary creatures. I'm obviously talking about the table in the second stage of the first map, but there are other places you could loop them in.
Wait for Them by the Side of a Door
All you need to do is stand right next to a door, wait for them to enter your room, and exit it while they're still getting inside. Since CAPCOM had the brilliant idea to lock the bioweapons in a dumb animation while they're going through doors, there's nothing they can do to stop you as they can't move until the animation is over.
This method can be repeated indefinitely and works 100% of the time if executed properly.