Simply put, the Tier List is outdated, we are already working on a new one.
We are corrently working on a updated version of both of the tier lists, the last units heavily changed the meta.
Gokuuu didn't show up due to the equipment having multiple tags, right now it's mistakenly listed as being Goku-only. We'll fix that.
Krillin is defintely in a good tier. The analysis always show pros and cons even if said character is Top Tier.