One of the best parts of Test Your Metal event taking place at the same time as Over the Rainbow was that, if you happened to get Perseus or Nightbringer of your preferred weapon type from the Leprechauns, you could go back to Ferghus and pick a different Fergseus weapon type. This made it so TYM event wasn't useless even if you got the same or better tier of weapon from OTR, as you could give yourself a push for yet another weapon type.
With the newly changed event dates, it's completely possible to pick a Fergseus weapon, and then after TYM has ended get the same weapon type from OTR which makes the Fergseus instantly outclassed.
My suggestion is that TYM event be extended as well. Could just make it so you can change your Fergseus weapon type and re-upgrade it until OTR is over. If the availability window becoming too long is a problem, you could make it so that joining TYM is only possible during its original intended runtime, but switching and re-upgrading the weapon can be done for a bit longer.
This would make up for the mismatch in the events' availability windows, therefore better compensating for the time during which OTR was suspended.