A similar new feature request has been resolved as won't fix, but the reasoning for the "won't fix" determination has a problem with it.
It is pointed out in the won't fix resolution that the Links Hierarchy plugin covers the functionality requested, but it does not for the following reason. The "blocks" links typically form a directed-acyclic-graph, not a tree. A DAG can have the following structure:
The Links Hierarchy Plug-in does not handle this case well. It shows multiples of E and F, one hanging off C and one off D.
PERT charts are a long-established and valuable project issue/task dependency management tool, and JIRA needs one.
I will be forced to hand-copy my issues into Visio bubbles and arrows until this feature happens in JIRA.