i read in another thread someone was talking about cluster bombs giving single digit frames, and he mentioned a potential solution about different explosion effect for cluster bombs/submunition dispensers. i think that would work.
currently, explosions are more of less procedurally generated. each weapon is assigned a few values such as explosion radius, size, dust generation, etc. for a cluster bomb or submunitions, the game renders a few hundred instances of smaller versions of those same particle effects, nearly simultaneously.