Yikes. This would feel a little fairer on a creature rather than an enchantment. In a dedicated deck this will be "No creatures for you" even more quickly than Call to the Grave or suchlike.

Alternatively, at least give it a self-sacrifice clause like Call to the Grave / Pestilence / Porphyry Nodes / etc.

This is meant to be one of the pushes to make Dementia an alluring draft strategy (like Hand of the Praetors). Given that Dementia seems even harder to draft well than Infect (it's in three colors), I think the rare bomb is fairly justified.