I have a somewhat low opinion of MMOs on a fundamental level, actually. They milk their subscribers for money by absurdly extending the leveling curve and requiring significant amounts of farming or repetitive missions. That's not why I play video games.
Needless to say, you can imagine how I feel about Yiazmat. If that's fun to you I have no problem with it, but I can unequivocally say it would be a huge waste of time for me. Why not give it a trillion HP if it's really that fun? It doesn't take too much to make a game difficult or long (just modifying some numbers), so I value design much more than either of those two, though they are part of it.
Though I do agree it wasn't that long... about three minutes, if I recall. But when I'm fighting a boss I don't want to spend three minutes not doing anything. It isn't even as if I have to fight for my life while I wait for it to become vulnerable; I pretty much just sat there.