The previous event with the 'Digging mini game' + the May/Winter events with the 'Shuffleboard' are
light years easier to obtain all 9 artifacts, if you know what you're doing and how to properly exploit those games.
The '3 rotating chests' is generally down entirely to the RNG if you'll make it or not, since you
must collect +X amount of bonus currency from the chests to hit the 260 GP pts.
You can complete the entire quest line, AND, get the 100 e-mail bonus, AND, log-in every 3-4hrs for maximum incident pick-ups, yet still fall short in the 3 rotating chests if you get really RNG-screwed... that's simply because the 3x rotating chest events only give you 'X' total currency, but you need to make 'X + Y = Z', with 'Y' being the amount of bonus currency you must add-on from the randumb chest wins.
On the other hand, if you use your tools well in both the digging + shuffleboard style events, you can fairly easily hit your 260 GP pts and claim all 9 artifacts, even pushing well into mid-upper Silver league for 0 diamonds.
TL
R version; the 3 rotating chests are the WORST events because you absolutely
need to rely on the RNG luck factor. To hell with skill - even if you know exactly which chests are the most efficient, if you get enough bad rotations and/or can't win any bonus currency, you're never getting all 9 artifacts without spending some diamonds.