Timeless Isle Gear
Timeless isle drops armor tokens that can be converted to ilevel 496 items with random stats (like heroic scenario gear)
These tokens can be upgraded to ilevel 535 using a burden of eternity
burden of eternity can be obtained:
From a blazing chest (100 % drop rate, but one time per character),
From random drops from timeless isle mobs (low drop rate, but repeatable)
By turning in this quest (guaranteed, but one time only),
By opening a chest around Master Kukuru at a cost of 500 timeless coins (low drop rate, but fixed cost and repeatable),
By spending 50,000 timeless isle coins (100% drop rate, high fixed cost, repeatable).
Most efficient way of obtaining a burden of eternity
Other than the quest and the blazing chest, the most efficient way to obtain the burden's of eternity appears to be spending 500 timeless isle coins and looting the chest near Master Kukuru.
Conclusion
If you are already heroic geared in all slots, you probably won't find an upgrade on the timeless isle and we all hate you even if it is an irrational hate.
If you have a few ToT LFR slots to replace, you should just loot a blazing chest and complete the quest for your burdens of eternity, and then hope you get armor token drops from the activities on the isle.
For those that need more than 2 slots upgraded and for alts, get the two upgrades from the chest and the quest, then grind timeless coins and spend them with Master Kukuru.