This is related to my earlier question, Superman in Dresden Files. Cliff's notes, my players in DF take the building block powers, and I wanted to know why and what to do about it. That gave me a decent idea of why my players might want Mythic powers, and along with other things convinced me to relax my ban on such things. However, from a gameplay perspective, I still have an issue with them I'm now trying to solve. How do I design encounters for these characters that are not shutouts in either direction?
The Mythic powers are actually well balanced in a way. They make characters very absurdly strong in one way, and one way only. I can easily take these characters apart. I can also easily create challenges they walk through. What I haven't figured out to do is anything remotely between.
On the hard end of the scale- Most Mythic powers have a catch, a weakness that cuts through it. Simply finding an opponent who has knowledge of and access to the catch works to completely negate the majority of their refresh expenditure, and leads to them getting demolished by opponents who can use their own powers. They strongly dislike this. Even if narritively it makes perfect sense their enemies would do this, they dislike spending so many points on being tough only to have it ignored. Reasonable.
I can also put them in situations where their powers are not useful- For example, none of these powers help them at all in a debate, or in tracking down an escaped criminal, or in solving a who-dunnit, or in healing a grievously wounded comrade. They don't dislike this, but they disengage. Despite the debate being literally about whether to throw them and certain friendly NPCs all out the airlock as abominations, they were clearly not engaged with or interested in the game during the debate. Once the mob decided to go with the airlock, then they engaged- into scattering the crowd like ninepins and brawling with the Wardens who had stirred up the mob.
I've found that spellcasters or especially resourceful rich people (cough Marcone cough) can also counter the powers. Lifting a mythically strong hero into the air with a spell works remarkably effectively. Supernatural Toughness does not protect you from being drowned, and speed is of little use against solid enough armor. They usually decry this as being cheap and frustrating.
I can create consequences for the use of their powers- they get a reputation, the mortal authorities get involved. However, for this to have narrative teeth, this has to lead to an actual consequence of some kind, and this group has expressed the opinion that the police are "cute." Showing off has alerted more foes to their location, but that leads to more combat, which exacerbates this problem. It's lead to challenging conversations with friendly NPCs trying to get them to tone it down- but they tend to tune out of social combat, and if it's not combat, it's roleplaying, which both they and I enjoy. So, haven't found a consequence that was actually a consequence yet.
Lastly, I can simply create antagonists with the same powerset as the players- but this has the effect of cancelling out both powersets, leading to boring play over the long haul. Such mirror-matches were fun once or twice, for both me and the players, but I'd rather not endlessly churn out copies of the same two or three powersets.
Of course, if I do none of these things, then my players have a very easy time of things. That's what those powers are for- when not negated in some way, they make you peerless at what you do. What challenges can be created for such characters that are not hopelessly onesided in one direction or the other? (Note: By challenges, I do not mean only combat, but they have expressed disinterest in challenges where they cannot use their special powers. That's probably going to be a hard sell. Pulpy, actiony non-combat will probably work better, if I could keep the game moving fast.)