Was just thinking on it, and I've noticed to anyone with a decent number of cards, sudden death kicks in while still drawing. I had managed to run a raid enemy out of cards, and my heroes were crossing the field, a guaranteed win, a legitimate strategy.....and then the sudden death kicks in, defeating me. Just a thought, but maybe it shouldn't kick in until all involved in a fight are out of cards? I mean, don't get me wrong, as is it certainly benefits the ai, who always seems to get it cards/heroes out in a swift and efficient manner, but for those of us who have long wait times to summon, drawing the battle out is a legit strategy, one countered by an oversight.
The sudden death seems a way to finish a fight, especially if say both the player and ai are out of heroes, but in that case, it should be activated when needed, when out of heroes/cards, not just set at a round randomly chosen.