I think we need more "sleeping sentry".
That 1 trechery or shadow effects per adventure that tells you 'keep this card in mind, or you lose'
Trechery cards deserve as much attention as enemies and locations when building a deck, yet most decks are more about 'yeah let's kill giant spiders and orc chieftan, slaying legendary Balrog and Watcher or two along the way' than 'let's watch out for trechery of our enemy'.
Back in core set days, I needed to really watch who to quest and who to exhaust, how many hit points remained in my heroes because of direct damage cards (Orcs… Necro's Reach… Hummer shadow).
But when playing Mirkwood Cycle without Dol Guldur Orc set, Dwarrowdelf Cycle without Hazard of the Deep set, and Massing at Osgiliath, there is no tension at all, because all your questing characters are safe.
What we need is a way for each sphere to be able to prepare for Trechery cards (so far Spirit and Lore are only ones to have it), and couple of really nasty trecheries per pack that needs to be dealt in different ways (like Sudden Pitfall, I like it in a way it forces you to not quest until you get atleast 1 questing ally, and not defend with hero without a cancel trechery.. just changes the way I play).