The chance of missing a giant chaos bolt is much smaller than the 0.05% or whatever because you probably only spend a fraction of your casts on them.
Really, people who MUST hit cap are either OCD or misinformed about statistics.
To those who argue that missing a spell may cause a wipe and thus you are selfish for 'maxing your recounts,' I counter with this:
By choosing to over-cap hit instead of maximizing your DPS, you are selfish because you are increasing the likelihood of a wipe by the ratio of possible average dps compared to your lower hitcapped dps.
You'll probably never notice a spell miss even with .13% or more below hit cap. I sure haven't. I've also tanked using stacking resilience trinkets to reach uncrit-ability, technically leaving me vulnerable to crits less than 1%of the time for about 5 seconds at the start of a boss fight. I've never wiped a raid due to insta-gib.
The chance for these things to occur is so infinitessimal that if it does happen once, I'd probably be more amused at the luck.