Draws don't happen often in any game really, but when they do, it only frustrates everyone. This happened to me in "Staffords Chapel". Assuming this could happen in PvP, most of my suggestions are for both PvP and PvAi. 01. Player Wins 02. AI wins 03. Coin Toss Wins 04. Most Stars Win 05. Most HP Wins 06. Most Characters on Board Wins 07. Done the most Damage Wins 08. Sudden Death - All Damage is instant kill (Advantage Mage) 09. Sudden Death - All HP Reduced to 1 (Advantage Cleric) 10. Sudden Death - +1 Environment Damage Every Turn 11. Sudden Death - Disable all Healing, Armor and Blocks 12. Sudden Death - Every Token Must roll 4+ Every Round or Die 13. Sudden Death - 1 Victory Square Appears on a Random Map Square 14. Sudden Death - 10 Neutral Imps Spawn in and Start Attacking Everyone Ni|
Round 29? That's nothing. I got to round 58 on the third map of Arena Finals the first time I played it, and I think I reached round 33 on the third map of MM16 just now. And really, I don't think it's a problem in the campaign. Annoying and tedious, yes, but still preferable to actually losing and having to start over. PvP has timers, so no game will ever last longer than 40 minutes (half that for most leagues). There are some concerns about stalemate situations, but that's mostly a map design issue.
I used to have a post on the topic but only about MP. It can easily happen on maps where VPs are far from each other and both players have 1 character sitting on them. Nobody can move and both players just pass for 100s of rounds straigth.