To begin, "Epic" was, as far as I can recall, randomly used once in a trade topic somewhere. People immediately liked the term, and started applying it to everything.
Now we have a tie between people that think Epic = random stats with 20+ IVs and Epic = High viable stats + good everything else. The SECOND was, if I remember correctly, how the original topic used it. The first? I have no idea who started applying it that way, but others saw it being used inappropriately and decided it was correct. They then continued to use it thinking what they were doing was right.
"Epic" has only ever been concretely defined once and before the dust could settle people ran off with it. I have yet to see that term in any other Pokemon-related game and the term has only been around a couple of years.
If you want to unanimously decide on something specific in this topic, then you guys can make it your goal to politely inform/occasionally remind others what it means if applied incorrectly. After all, the wiki can be changed.
Otherwise, this is just gonna continue.