Originally Posted by
Oliria
Are we comparing 3 tier pieces + Krugruks with 4 pieces? To be a 100% sure you need to run this through simcraft, but my gut feeling tells me 4-set is better in this case. It is correct that the 4p bonus isn't amazing, but the only thing beating it is 2p+Warforged offset. Without the proper offset pieces, and without them being warforged, 4 set is still best.
Krugruks has hit/mastery, tier shoulders have expertise/mastery. I am almost certain that you want to use the 4 set in your case.
To clarify this is for heroic pieces, but can probably be applied to any gear rating:
2set+heroic warforged offset > 4set > 2set + heroic offset pieces