I'd suggest the strikes shouldn't be treated in isolation to the situation as a whole. Yesterday was a problem because Southern is so understaffed. The levels of sickness and lack of cover being provided could be partly attributed to the dispute, even if it wasn't officially a strike day.
I deal with Southern every day and my experiences getting to and from Falmer this season have just been an extension of what I deal with on my commute.
Now, I'm generally sympathetic to union causes, but in this case RMT are one of the players at fault for actively choosing to hurt local...