Piercing wand makes it a joke. I just did a quick reminder run (which was rushed and very poorly played), and I managed to get him down to 136 hp. If I had found the piercing wand or not been rushing (hence missing a couple ridiculously painful and obvious mistakes), I would have won. It isn't particularly hard or interesting.
As for monk, I think it would be more interesting if the boss had less hp and much more damage. So you have to be able to spell cast or just have a ridiculous amount of resists and power. Something like the normal SMM hp (1200 or so?) and 200-250 damage.
Warlord stretches your character, but not in an interesting way. The goat horns are fun and not really interesting sure, but they are necessary. Frankly, the most interesting golds (IMO) are the one that stretches your character class, and what hurts a warlord more than monsters with DP? What if every monster got a level of DP when you leveled up (making you go for higher level kills and hurting the normal warlord strategy), and in turn something else was nerfed?
I speak chaos.