So my guild can complete t6 of the sith raid in four days. Are we to the point where we should try the heroic lvl? How high does a guilds GP have to be?
If completing tier 6 in 4 days, you are far from ready. Even if that was before the recent huge nerf to boss health on tier 6, you probably wouldn't be ready.
However, if you make an attempt on heroic you will know how far away (or close) you ate to being ready. That's always a good thing to do when preoaring