You don’t seem to understand me. Effective (The mechanic) IS just a 1.25x boost. The Effective Mythic Affix changes your element to whatever one that will give you this boost. The affix does not affect resist at all. Play an Ice Map with 100% Immune, look for a Fire Fury and hit it with Effective. You will see that you deal no damage. Then compare the damage of Ignore Resist and Ignore Resist + Effective against that monster. I recommend using something like Iceburn Set to reduce the default +/-25% DMG variance.
Weaken is bugged atm so I will have to look at it in more detail.
I will look into equality later but as seen in the dictionary, Skilled only works with MH skills. The other descriptions failed to update with the dictionary (game engine is old and you need to update everything manually).
Edit: Also Skilled is intended to not show up in the stat page since it changes depending on the situation (Discordance).