So, this is going to be about choice. Usually in bossfights you don't have one. You can make a tactical decision but not choice that a changes the fight entirely. The closest thing to choice in a bossfight is Flame Leviathan. You choose how many towers are hindering you with additional obstacles, but that's it. The Leviathan itself does not change and

what you do to beat him doesn't either.

The Assembly is different in that regard and somewhat refreshing. The kill order actually changes the fight. It

's not like you kill 1 mob first because t

hat is the easiest for you to do or because he is the biggest hassle. Depending on the order you take either Brundir, Molgeim or Steelbreaker out of the picture the remaining become different to fight. They get new abilities and every one has his own combination of those. It's somewhat like the dragons you pilot in Occulus. When you reach the final boss, every dragon has his full set of abilities.

For the Assembly of Iron it works the same way, just that the boss mobs get their abilities and not you. Molgeim and his lightning tentacles are fairly easy. Molgeim last means nasty, little, exploding elementals. And when Steelbreaker is the sole survivor in the fight he becomes a Brutallus clone with a Vaelastrasz complex and a build-in Gruul-ability. That's a three bosses in one. Not only will he be hitting like truck and trying to clobber your best tanks back into the Barrens, on top he is also fed up with one tank rather quickly and decides to simply blow him up. And as icing on the cake, whenever he kills a tank he also "levels up" (seems for him a level 80 player provides enough XP).

That is quite a choice one is making there. Turning the fight from beating up a gimpy dwarf to having a DPS race with a complex ladden Giant...