Lag issues?

I'm experiencing about 1 second delay b4 my slaves will assist my focus, is this normal? In instances it seems to be more like 1.5 seconds which is weird. I was thinking about setting up FTL, does this help with lag issues at all.

An example is when a target is near dead, then I'll switch to another, but when I go to cast on the new target my slaves will remain casting on the old one instead. my ping is only 70ms, I can't understand why it takes sometimes 1.5 seconds for my slaves to get the new target.

(edit: i guess it makes sense, takes time for my input to get to the server, then my slaves get it from the server which would essentially double the time? Could be wrong lol)

this is something you will get used to over time and affects both focus targeting and FTL setup.
as you mentioned it is indeed the time it takes for wow to send your target to the server and than your slaves receiving that. it also doesnt seem to be affected much by your ping.