First time to both write a deck guide and attempt to theorycraft, so please indulge me. This is a hopeful albeit quixotic attempt in making "Seek Guidance" work. The quest is very hard to complete but I reckon that pulling it off will be 10x more satisfying than using Yogg Saron or C'thun to kill the opponent.

Retain the quest card for T1, mulligan for cards for T2-T4. New cards like Pandaren Importer and Entrapped Sorceress are crucial in the initial turns due to their card generation abilities.

Depending on your next card draws, take advantage of the discover effects of cards and choose those with the card cost that will help finish the succeeding questlines. With some luck, draw Taelan during midgame to tutor Primordial Protector that will then tutor Soul Mirror to help you in the quest. If you're facing a slow deck, you may want to keep Taelan during the mulligan.

New expansion cards like Void Shard and City Architect will bolster defense. Combined with the usual suspects (Renew, Apotheosis, etc.), fingers crossed, this deck will offer prolonged survival while threading the needle trying to execute the newest and fanciest kill card in HS.