I still not sure what effect dice do,
All outcomes of actions are rated as effects.
Eg if my action is to summon my magical power so I can use it to unleash a great sorcerious blast onto my enemy, then in mechanical terms I am attempting to create an Asset (Summoned Magical Energy) and, if I succeed in my action, I have created that asset rated at my effect die (in the fiction, imagine it like a panel from a Doctor Strange comic where a wizard is holding a ball of energy in his/her hands). When I then use my Mystical Blast power to attack my foe, I can add the Asset into my pool, which gives me a bigger pool as per my post above.
Suppose my Mysical Blast attack succeeds, then the outcome is also an effect die. In Marvel Heroic (again, I'm not sure about other Cortex variants) if that is stepped up above d12 then the opponent is taken out of hte conflict; otherwise it sits on the opponent as a "trait" which can then be incorporated into dice pools for actions taken against them (ie MHRP the way a debuff works is that it adds a bonus die to an opponent's pool). This means that having a d10 or d12 complication or injury is a bad thing, because all your opponents are getting to add that d10 or d12 to eir pools, even if they are otherwise fairly ordinary foes with abilities rated at d6 and d8.
In attrition-based conflict systems (eg D&D hit points) it often doesn't make sense to spend an action building up an augmentation for a future action, because the buff isn't worth not getting the chance to wear away some hp/life force/whatever. But MHRP isn't attrition-based. If a foe has (say) a d6 Grappled complication and then I succeed again in grappling them with a d10 effect die, the d6 complication is replaced by my d10. So my d10 is not more effective than it would have been if they had had no prior complication. (The exception to this: if the new effect is rated the same as or smaller than the existing effect then it steps that up: so if the opponent was under a d12 Grappled complication and then I successfully grapple with a d6 effect, that is enough to step the effect up above d12 which takes the opponent out of the scene - in this case I might narrate that I've completely immobilised them, or successfully applied choke-hold, or whatever lese makes sense in the fiction). This is why having d10s and d12s in pools is so useful from the point of view of generating effects, and also why spending a term to build up an asset so as to grow your next pool can make plenty of sense.
It also explains Sunsword's complaint:
This was the source of a good deal of frustration in the game I played in. Since Marvel characters can easily have a d12 conflicts ended quickly and were fairly boring. I'm not saying we were playing everything the right way but it did leave a sour taste in my mouth.
I can see what you mean here. It's not something we've experienced too much of, even in games with characters whose abilities are rated at d12, but I can see how it could happen especially eg if you've got multple d12 Strength or Weapon characters getting into a lot of melee-type fights against opponents with no Stamina-based SFX to shrug off those hits.
To keep replying to
@Tonguez: because the system is not attrition based, a character with d12 Godlike Strength who succeeds on an action to punch someone can fairly easily have a d12 effect die which might (due to various factors, eg think back to how I statted up Glamdring for Gandalf) step up to d12+ which is an instant take-out (because take-out is based on effect rating, not attrition). This is what is happening in Sunsword's game which is making for boring conflicts.
Like I said just above, I personally haven't found this to be a big issue but I can see how it might happen with a particular group of characters in the right sort of conflicts. My general advice would be, at the start of a campaign, to not have PCs with d12 ratings. Let these be earned through play. Then the growth of those dice pools will correspond more to the growth of the campaign towards a resolution.
A final thought/comment, building on the prevous paragraph: I think Cortex+ works better for short-to-medium length arcs (eg a few to maybe a dozen sessions) rather than years-long D&D style 1st-to-20th level campaigns.
