the next version would have a solid two-piece bonus

Traditionally, Blizzard follows WOW Gold a very well-crafted pattern when designing the set bonuses for each of our new sets. If a set had a particularly strong four-piece bonus, then the next version would have a solid two-piece bonus and vice-versa. It's all a delicate balancing act that keeps upgrades as upgrades.

Unfortunately, we've run slightly amiss of this perfect level of balance this time around. While tier 13 isn't bad by any mark, the bonuses that you get out of tier 12 are extremely good -- so good, in fact, that there are times when it isn't worth upgrading. The standard rule of not breaking one set bonus until you have the next does apply, but in this case, there is one more nuance to add to the list.

Tier 13 is only a solid upgrade if you match levels. This is to say, the Dungeon Finder level of tier is not a good replace for normal mode, and normal-mode gear doesn't quite replace heroic. If you manage to collect all four pieces, then it can be an upgrade WOW Gold, but don't break your old four-piece for the new two-piece unless the set types match.