It seems that in the most recent "global 6% cooldown increase", Tesla bullets (and presumably other items as well), were accidentally nerfed from a ~0.3s internal cooldown (maybe 0.35?), up to 0.6.
One theory is that the 6% increase was rounded to the nearest 0.25, meaning that 0.35 had 0.25 added to it, effectively nearly doubling its cooldown instead of just being a minor bump.
One theory is that the 6% increase was rounded to the nearest 0.25, meaning that 0.35 had 0.25 added to it, effectively nearly doubling its cooldown instead of just being a minor bump.