I’ve been using the OL system for a while now, and I’ve noticed a couple of issues with dice explosions and their results.
Massive Explosions and exceptional success devalue bane attacks. With a massive explosion, not only do you deal massive damage, you also get to apply a bane as bonus. With a bane attack, you don’t do more damage, the bane isn’t more effective, nor is it harder to resist. You could roll a 50 on a bane invoke just to have it resisted before it even does something. It’s not so much that bane attacks are useless (though I would argue some become obsolete once you reach higher attribute scores), but a massive dice explosion should feel good when making a bane attack, not give players a feeling of “damn, that could have been damage”.
Same for boons. Like with banes, no matter how high you roll, boons always have the same effect (as long as it’s over the required PL). Sure it’s still a success, but every explosion here is accompanied by a feeling of “that could have been more”.
They can escalate too much (in my opinion). I’ve seen it and I’ve heard it from other people, including GMs. You plan out a tanky character or an epic boss, only to have it get killed in 2 hits due to some ridiculous explosions.
Solutions I would suggest :
Exceptional success could use a bit of tweaking. Bonus banes could be limited to half the attribute score. (possible exception of bane focus). I might even go as far as to put an upper limit on how much damage a single attack can do based on the attribute score, but that feels a bit like a hamfisted solution.
Banes and boons could also use some rules/guidelines when it comes to exceptional success and bonus effects. I suggest something along the lines of invoking at a higher PL, a free sustain for a round, an automatic failed resist/disadvantage on resist rolls.