I like the new information. Normally I'm more supportive of Plarium and less likeky to hard on mistakes. However, the extra broken gear is a mistake if rolled out this way.
A better plan would be to have increasing chances starting at gold 3 or 4. As it is now, people say the rewards for plat aren't enough change to grind your way past gold 4. But if you give insane gear away to plat players, that gear is crazy enough to make sure no one will get to platinum from gold 4 after a few weeks.
I suggest a small chance at gold 3, little better chance at gold 4, and increase from there.
Another suggestion, make a single relic set. If one weapon is a level higher than a 2-pc set, it acts as both trophy and gear. Maybe a notch better than a 2-pc set, but not tons. That allows plat players to have something no one else has, potentialy without locking nonplat plyers out of a chance to ascend.
Third, those sets shouldn't be so god-awful powerful. Arena competition should be driven by parity. Best players should have a chance to compete with their stuff, not locked out of competition. The current game runs on collectible luck, combinations, and real time strategy. Part of that is build choice. Do i use the cruel set? Or divine speed? Or crit damage? If you instead give me higher speed than anyone can get in a 2 set, and more crit damage than anyone can get in a 2 set, and then give me a chance at unkillable when a good player finally kills one of my team, how can i be beaten by someone who has to choose?
This will also impact team composition, creating a single tier hegemony, which is bad for the game. You don't want to discourage people from playing because they 6-starred Serris and now she causes no damage and has fear reflected back on her. Or people trashing all their atk champs because you can't compete against extra hp and 20% def and being damaged by your own bombs every single game. You should reward a wide array of team comps and these rewards will do the opposite.
There have to be better ways to reward great players without locking f2p and casual (but committed) players out of the game's top level. If not, you'll lose platyers.
I also think you shouldn't have more new champs without a new story mission and maybe a champion design contest. You need excited players and currently there's a lot of grump. If you tell me i'll never be platinum because i can only fight faster high crit rotos with another unkillable option to get past gold 4, the game will get boring or frustrating.
The potion fix is fine and the 90-120 days bit is great.