Actually the deletion of email was enough "evidence" of guilt because legally it can be assumed that doing so is evidence of guilt.
She only deleted those deemed "personal". It's true some non-personal ones actually also got deleted, but there's no evidence it was intentional.
Electronically recovered versions of the "mis-deleted" ones showed no signs of a pattern to hide, but rather sloppiness/laziness in filtering, being the "skipped" ones had trivial topics. Comey said it appeared that whoever filtered the emails for personal-vs-work only read the title and maybe the first few lines rather than the entire message to see if it were work-related.
Again, there is clear evidence of sloppiness, but NOT of "intent" to hide.
If anything, there's the opposite because those electronically recovered after the fact did not reveal any "secret pattern" to the deletion. It's true they couldn't recover all the emails, but those who deleted them wouldn't know which of the personal-deleted set would wind up being eventually recovered in the lab.
Thus, there is actually counter-evidence of intentional hiding, because the FBI got to sample some of those intentionally deleted (for allegedly being "personal" when in fact they were not).