But it is my job to make combat fun - to me that includes that the fights have to have some sort of tension to them. The characters don't have to be on the risk of dying all the time - but they have to fear the risk of dying every fight.
So, it sounds like you haven't actually run any Dungeon World combat yet. One thing you'll learn is that the PCs are generally very powerful, and that you as DM will have to learn a few new tricks to make things challenging. The example people new to DW usually point to and freak out about is that the standard dragon only has 16hp. Even with 5 armor, if you let the PCs just stand there and wail on it, it goes down in a couple rounds.
Making combat fun in DW is generally not about hit points. For one, I think experience in other games is making you overvalue "whittling away hp" as a threat, and also to *undervalue* the -1 from gaining a debility. A -1 in DW, rolling on 2d6 and looking to roll a 10+, is more like -4 or even -5 in a d20 game. Plus, hit points are easy to recover, and debilities are hard.
Consider: the Cleric and the Bard both have Cure spells that restore d8 hit points, and there is nothing in the rules to prevent a character from sitting there and just casting that spell over and over and over again after every encounter. Note, I said nothing *in the rules* -- what prevents it is that eventually they will roll a failure. It is your job as GM to give them a healthy fear of that failure. Not so much fear that they just want to stay home, but enough that they think about it every time they pick up the dice.
So: how *do* you make combat interesting? Cinematic tricks are good: making fights about more than just standing and slugging. Set fire to things. Open cracks in the earth. Make them run and gun. Smart enemies are good: have them threaten things that characters have to worry about. (Ok, Paladin, do you hit the goblin in front of you and let the other two run past to tackle the princess, or do you block those two and let this one have a shot at your back?)
If you haven't done so, I highly recommend reading:
The Dungeon World Guide:
https://dl.dropboxusercontent.com/u/3269630/dwdotcom/eon-guide/Dungeon%20World%20Guide%20pdf%20version%201.2.pdfThe 16hp Dragon:
http://www.latorra.org/2012/05/15/a-16-hp-dragon/This is all leaving aside another point: other things players can do with those multiclass moves include: Learn to cast spells like a Wizard; Learn to cast spells like a Cleric; Learn to shapeshift like a Druid; Deal +1d4 damage (all the time) like a Merciless Fighter. It's far from obvious to me that Bloody Aegis is even the most powerful option available.