What I find funny about the mythic proficiency is that inversely scales with level to a certain extent.
If you are level 2 and use rewrite fate to re-roll a saving throw with mythic proficiency and are only trained in the skill then you get an equivalent of a +8 to that save (& a reroll) if you are levl 15 and legendary in that save you get a +2. Now a +2 and a reroll is still really really good but a +8 plus a reroll is insane so rewrite fate at least is going to have less of a wow factor as you level.
