Of the three DLCs for Dark Souls II, this is probably the worst in terms of level and encounter design. That being said, the level design is still miles ahead of the base game, and despite their obnoxious configurations, most of the new enemies are fun to fight one-on-one (I especially enjoyed the giant guys who have lava pouring out of their shoulders to punish circle strafing). Most significantly, two of three new bosses here are among the the best in the series. Sir Alonne is a tense and challenging honor duel who somehow makes his deplorable boss run completely worth it. And the Fume Knight is another superb one-on-one fight with a clever mechanic tied into level exploration. These two bosses alone make the expansion worth your time (the third boss is a lazy reskin of the Smelter Demon tucked away at the end of one of the ridiculously hostile challenge areas that were apparently obligatory in all of the DSII DLCS). Add on some level exploration that is very good (even if it’s not quite as strong as Shulva or Frozen Eleum Loyce) and you have a quality expansion that anyone who picks up Dark Souls II should definitely play.

The 2nd of Dark Souls 2's DLC's, I would say this is it's strongest. It continues the theme of the previous DLC, in that it takes the standard Souls formulae in a more experimental direction. While Souls games have you exploring vast areas which interlock and twist around on themselves, this DLC instead has you explore and work your way down a huge, sky-scraper-esk tower. Going down level by level in exploration which is often more vertical than horizontal. This does make it feel relatively linear however.

The developers were able to stretch their creative wings with this DLC, with a great mix of creative enemies and environmental hazards, which mix well with each other. For example, enemies who will explode if they are touched by fire, inside of a room with multiple fire-spouts, forcing the player to be careful and strategic with how they engage, rather than simply running in and swinging.

And while this DLC does still contain 1 very bad boss, the other 2 bosses are great, easily among the best in the game, and for some potentially within the top of the entire series.

Unlike the sunken King DLC, the Iron King DLC actually has a good story, with interesting characters who tie into the plot o the base-game.

A uniquely designed DLC, with creative enemies, a fun story, great bosses, and is just long enough to enjoy without overstaying it's welcome, it is a marked improvement and probably the best DLC in Dark Souls 2.

Y'know, this one wasn't as bad as the Sunken King. It had some shitty moments like the boss run to Sir Allone, but that was manageable after grinding down some of those annoying knights. Blue Smelter Demon was one of my favorite boss fights in a weird way. Incredibly difficult for me, yet so engaging despite it's clockwork nature. It might be the hardest Dark Souls II boss fight for me if I'm being honest. It doesn't help that the runback for that one is a special kinda of hellish that I didn't grind down. And finally, Fume Knight was pretty fun! I actually found it to be the easiest boss fight in this DLC, but still a great time. I also loved how easy the boss runback was for this fight.
The DLC focuses on what DS2 does best, knight boss fights. It doesn't reach the heights of Artorias of the Abyss and the level design is still frustrating at times, but not nearly as bad as The Sunken King DLC. It's better than most DS2 levels or bosses, but still not enough to really kick it up a notch for me. Worth playing in some sense, but it's still DS2 at its crappy, contrarian core.