That anime is not silly enough to tell us that novas are Pandoras that lost control... or Pandoras that evolved with no limiter, or lost their limiter and had an energy boost or something like that...

Suicide mission? and very self centered indivudals. Something's not right here.
It's true that we know of two pandoras who died eliminating a nova. But we do not have the full picture yet.
Moreover, those 2 pandoras were protecting their comrades, which does not fit. But maybe it's to tell us they were in fact not efficient enough, precisely because they died protecting others... but in the end, they are warriors made to protect the population.

Also, they seem to work in groups of 3 or 4, they know friendship, even the bullying ones. Or so they seem.
It's just they are quite violent and fight for any reason.
It might be an after effect of their transformation and growing power.