Cylinder is skill specific and so it's cast % of 0 would multiply with Phen's cast %.
I use throwaway accessories on my gen tbh, and at the risk of repeating myself, the sheriff badge is a p good alternative to other thing -- especially if you want to put a phen card in something that still gives you damage (though PoM is great too and serves additional utility.)
However when I get slow cast, my cast time for CC really really sucks for my level 140 gene