I have like 2 or 3 Brimstones, one of which dropped while farming for the Worldeater, presumably just to mock me. Looking it up on grimtools, I’m starting to think it’s a bit pointless to continue, because apart from the +1 to soldier skills and the casting speed, which I can make up (somewhat) painlessly, the non-MI legendary might actually be better for my fire forcewave commando. (Already have full conversion from other stuff.) 
Or am I missing something?
I prefer Worldeater for my Fire Forcewave Commando, makes it easier to cap casting speed and the chaos resistance is nice too, it means I can potentially free up a medal or amulet slot or something for an Arcane Spark (for some more OA) or something else, whereas I otherwise might have to consider a Black Tallow.
What I like about Worldeater though is the granted skill. I have it tied to Meteor Shower as the cooldown for the two is fairly close. It means I can keep Meteors going constantly and the projectiles are good at clearing trash, chunk gangs of heroes that like to gather around me and it shotguns large targets quite nicely.
If you don’t have to worry about chaos resistance or casting speed though, Brimstone might be the better choice. Brimstone is suited to stacking large Burns with Cadence though so using it on Forcewave is probably wasting it’s potential :undecided:
All that’s true, though I’m close to cap (like only teens away) without Worldeater.
Have you tried the Brimstone’s proc? The Worldeater’s skill sounds great, but is it that much better, especially since you’d have to stop and cast it? I mean Rain of Fire just happens.
I haven’t tried it no, can’t give any advice on Brimstone unfortunately :undecided:. My setup needs Worldeater to cap casting speed so Brimstone is a straight loss in DPS.
You’re probably right, anyway. I like my Brimstone fine, but Worldeater will be better one day. I imagine it’ll be a little more active; Brimstone is perfectly suited for half-asleep brainless play, but it sounds like performance will probably go up with Worldeater. Thanks for the firsthand information. 
Back to farming!
If you are fire-based then you will want “Worldeater”. Infernal Brimstone in AoM has no % physical converted to fire and the proc doesn’t make up for it.
You also get more + skills from Worldeater.