I agree, the process tree is broken.
We have come up against this same issue. It seems that the Approval process is mostly just that, only for approvals. The only concession for denying a request seems to be when ALL members vote No. We also end up with tickets in limbo.
There is a setting for the minimum number of approvers within a board, but there also needs to be a setting for the minimum number of deniers.
Did you open a support request or a new feature request ?