I'll be honest, I don't think Campaign Play would make a good tournament. If you're going to go with a Tournament format, I recommend sticking with Epic Play variants. Then instead of having each dedicated Overlord stick with a single hero group, assign each overlord a set of quests that they will know inside and out and how best to adapt to different parties. I'd go through and hand-pick quests which don't seem to clearly favor one side over the other. Then make sure that everyone has to play the same quest/overlord combos as everyone else.
Some example awards:
Win the quest: 10 points
For quests with 2 encounters, up to 5 points for the 1st encounter if they win. (Some quests may have different conditions, e.g. In a Fat Goblin, up to 5 points for the first encounter. 1 point per bundle saved, 1 extra point if they get all 4)
For larger quests with only 1 encounter (like interludes), maybe award 15 points for winning the quest.
For every 50 (or 100?) gold earned during the quest, 1 point.
If you want to add "progression" to the tournament, I'd say start the first few quests as Basic (Intro + 2 Act I), then move up to Advanced for a few quests (1 Act I, an Interlude, 1 Act II), then Epic for the last few (2 Act II, Finale). (Each Overlord would have 1 quest assigned to them at each level) But each individual quest is an isolated event.
If you really want to encourage more overall builds, you could restrict the upgrades from each section to build on the last one. So in transitioning from Advanced to Expert, they get 3 additional experience and an additional 100 gold instead of starting from scratch with 6 XP and 250 gold. (Note that this is NOT how these values are balanced, and may lean things in favor of the Overlords, unless you do the same to them, as they'll have had a chance to see each of the parties before moving on to the next level of play.)
Remember that in tournament play, you almost always want to eliminate as many variables as possible. If you want people to take your events seriously, you'll make a point of eliminating things that could lean in favor of a single group for the entire event (like getting stuck with a really nasty or really pushover overlord). I would probably also avoid the Conversion Kit and just stick with the base game and possibly even expansions (but I think you could probably save those for a second tournament).
Best of luck and let us know how it goes.
Edited by griton, 04 November 2013 - 11:43 AM.