Altar of Devastation Contract
+4% XP Shrine Rental Contract*
Altar of Epic Rituals Contract
+5% XP Shrine Rental Contract*
Twelve Planescaller Contract
Xorian Navigator Contract: Xathrizopkrsis
Note that they DO have access to the 3% XP shrine contract. Also note that every item on the above list is a minor time-saver, nothing more and nothing less. Also also note that, even if someone really REALLY wants something from the above list, everything except the +5% XP shrine is available for Turbine Points at or before level 64.
The most compelling argument I've seen in this thread concerned guild drama: Someone's guild was having social problems, because person X felt guilty about holding back the guild, or person Y felt annoyed being shackled to a super-casual guild. The above numbers suggest this problem was, at least in Karranor's case, psychological.
There's still decay, though. What happens if five members of DOA suddenly stop playing? For thirty days, the guild has the same number of accounts in the decay rate formula, but it has only eight-ninths the rate of renown gain (assuming everyone else still plays the same amount).
To make a short story concise, if five members disappear, their equilibrium level temporarily drops from 63-64 down to 61-62.
Here's a question: Are you unable to renew contracts for which you're no longer eligible? Not that it matters much in this case: The only thing DOA would lose is their +3% XP shrine, and it sounds like they're casual enough to enjoy the leveling process, not try to tear through it at top speed.