What kind of false dichotomy is this? Luck should simply never be a factor, period. That has nothing to do with difficulty.
Anyway, bosses should be able to easily kill you the first time around but be significantly easier afterward when you figured out what they do. Or, depending on the pace of the battles and the nature of pre-battle preparation, you might be able to figure it out halfway through the battle and still win. The point is that they should kill you if you're not paying attention to the idiosyncrasies of the fight itself.
This is also opposed to creating some super-strategy that works on everything. If you make them harder just by increasing their stats then all you do is encourage heavy use of stat ups and stat downs on every single fight. And if those don't work then all you're doing is making the player grind. Both are pretty terrible design choices.
edited 17th May '11 6:56:05 AM by Clarste