DMing, art or science? Actually Mr Gygax had a few words to say about that at the beginning of the oridinal AD&D DM's guide but things have changed a bit since then.
4e promised a new era era of easy to balance encounters with all sorts of guidelines on how to put together challenging encounters which wouldn't end in a TPK.
Lovely theory but sadly practice seems to have prodced some rather different results.
Now I'm not compaining that the players in my campaign are all powergamers (although one of them is and we're sure WTOC have his copy of character builder bugged as each Errata and FAQ seems to unerringly nerf his selections :-) ) BUT and its a fairly big but if I follow the encounter design rules in the DMG the encounters are just far too easy. Seriously, we've not had a death save for months, and even longer for a failed death save.
Its not just my adventures either, they think LFR adventures on hard are too easy too.
I've tried all sorts of things so far, big encounters, small encounters, long encounters and short encounters. Most attempts at providing challenge have either failed (read walkover) or have ended up being long slogs.
In the current adventure I thought I'd finally cooked up a challenge. I hit them with a series of encounters of varying difficulties (including one with an infinite supply of minions) and for the finale a level 17 encounter ... for a level 9 party - that should be seriously hard.
So what happened? Well I'm still waiting for that death save to happen, one party member hit the deck (repeatedly) but was always on positive HP by the time his turn came around. Seriously, what do I have to do to challenge these characters, nuke them?
Well it turns out that our story has a happy ending after all. There's me getting all hung up on providing challenge and making sure things don't become boringly easy (I'm not actually trying to kill anyone) and it turns out that maybe I shouldn't be too worried after all. I exchanged a few emails with some of the players and the reports I've got back are that they are enjoying it and they do find it challenging. So keep going I guess, its an ever shifting equation but I might get it right in the end and as long as people are enjoying the ride that's all that really matters.