The first deck I built for this tournament was a Miskatonic / Shub / Yog deck that focused on rush investigation, deck search, recursion, and milling. Due to the slower nature of Highlander, I felt milling could be a viable strategy. I like the deck a lot. It's my first 3-faction deck and it's quite competitive, though not unbeatable.
As for Shub's deck-searching and Yog's card-recursion abilities, I thought those were a no-brainer (as was taking Doppelganger for my restricted card). Being able to repeatedly recycle Cursed Skull and A Single Glimpse, or picking Y'Golonac out of my deck on the first turn seemed like a great strategy for this variant.
Unlike the standard format, in Highlander it's difficult to achieve sustained character removal (one reason I believe we didn't see a lot of Cthulhu). This also makes destroying characters with invulnerability - like Y'Golonac - quite difficult.
Jhaelen wisely pointed out his experiences from playing with just a Core set and how some cards, namely Ravager from the Deep, can be very tough to get rid of when you only have 1 copy of a particular card in your deck. I felt being able to throw down an Ancient One early on and then do the rinse-repeat sacrifice on my opponent's characters would be too much for most decks to handle.
However…
I made my second deck - the one I used in the tournament - on a whim. I wanted something fast and fun. More importantly, I wanted to keep my other deck a secret in case no one else had figured out the goodness of Shub + Yog + Highlander (which apparently a few did).
I needed something to bring to our highlander test session the month prior so I took "Lo Pan's Panacea." Surprisingly, my Hastur / Syndicate deck did so well that day (undefeated in 8 straight), that I was starting to have second thoughts. Was my Hastur / Syndicate deck really that good, or were people sandbagging the test session (as I thought I was, I might add)?
I couldn't make up my mind until the morning of the event. I opted for the faster Hastur / Syndicate combo simply because I like those factions. We'll find out if it was the right choice…