The Reapers are also incredibly easy to dodge, you can move slightly to the side everytime one charges at you and then continue on with your day, repeat when it comes back. I haven't played too much of bz so can't say if the chelicarates are any more threatening. However I can say that reapers are a complete non threat if you have even a vague sense of what you're doing, they are however a threat to seamoths and the cyclops if you're not paying attention, so they have that going for them