I'm hoping launcher would keep itself working with Java 8 too. So far it's worked smoothly for me for very long time, but i hear some others have had issues with it. If i recall the launcher refused to start minecraft because of a minor hint from Java, caused by deprecated parameter -XX: PermSize. Java 8 does not want it when starting up, but it still works if you do have it. So is it FTB launcher being too picky with errors so to not even try to launch game? I don't know how you would go and remove the -XX: PermSize that launcher wants to auto-add, as there are no options for it.
edit: Spaces after XX: because : + P =
edit: Spaces after XX: because : + P =