Video of Hellhades breaking down player's concerns and frustrations about a number of recent decisions made by devs, including seeing long-term, high-spending players give up.

at 27:50 the guy on the right is speaking about mythicals and how they ignore resistance, what does he mean by that? 

pretty much exactly what it sounds like. when they added mythicals to the game, they introduced a new option that booking them could provide in addition to the standard damage%, buff/debuff%, and cooldown decrease; ignore 20% resistance. pretty much any skill that requires accuracy will have that included, with the end result that all (booked) mythicals will ignore a portion of their opponents' resistance.

hardly the worst decision we've seen out of plarium, but you do have to wonder what genius thought that was a good idea.

ah ya the 20% ignore from booking didnt even cross my mind, thought ive missed something major lol, as in they ignore resist totally xD

Ignoring 20% Resistance was more than enough to totally change the High Resistance Meta that used to exist at high level PVP.  I am not what I would consider high level PVP, but I am certainly end-game PVP.

My 820 Resistance Siphi has only 656 Resistance versus Mythcials, so she went from being almost immune to being debuffed to having Mythicals debuff her regularly.       

Not to mention they generally have high base stats and gain even more stats from blessings.

Had to do a few switches (yay 300 gems) but Lightning Cage sure has shot up in value lately. I know I'm extremely unlikely to build out certain supports with enough defensive stats + speed and RES so Cage really becomes nice for protecting Stoneskin. Might not apply to your Siphi situation, of course.