Just wondering what everyones views are on the best way to use these ?
IMO ordinary weapons don't really seem like the best use, as a lot of the time if you need to penetrate something it'll be more effective just switching weapon and getting a different damage type. I don't see the +1 Pen from mythic making much of a difference here.
Where mythic might be very useful on weapons is a ranged Cipher? A mythic Frostfall and mythic Essence Interrupter seems like a strong combo. If your Cipher isn't penetrating enough to do decent damage and isn't getting focus they're a waste of a party slot.
Heavy armour seems like a really good candidate for Mythic to get AR stacked nice and high. If you can get everything you're fighting down to 25% Pen it doesn't matter what your Pen is because you're going to outlast them so long as you have a bit of sustain.
Shields seem like a big no-no for mythic. +2 deflection is meh.