Like I previously stated, I like that GE5 needs city defence, these bonuses were pretty much useless and the game as it is now on live is not balanced at all. All goes in one direction, attack bonuses for attacking army and Arctic Orangery.
However the GE rewards as a whole need to be re-thought / redesigned. In GE 1-4 we have some useless artefacts like Victory Towers and several other not so good rewards. But please, just don't fragment everything, even ritual flames level 1 should be won as a whole item, not some fragments, is just depressing for starting players that they need to complete the expedition too many times to assemble a single ritual flame level 1.
The diamond earnings should be kept more or less the same in GE 1-4, maybe remove few of them, like one of the 50% chance to earn 25 or 50 diamonds, but nothing drastic like you did it.
Now to the Lost Temple: it's an amazing building, basically it rewards the player with both types of attack boosts, but please, remove it's temporary property. Make it permanent and unique - not being able to have more than one in your city. You might fragment only this building, make the fragments available only after the last gate of the map, with:
50% chance to earn 10 fragments
50% chance to earn 50 forge points
Once the player gathers all 200 fragments, he/she will get:
50% chance to earn 75 diamonds
50% chance to earn 50 forge points
Since the GE5 is so difficult, please understand that you need to motivate the players to go for it and since the most useful & best currency reward from the game are diamonds, you need to throw some for the last(and most important) reward of the Guild Expedition.
