I don't see these Relics right now as a good addition, but I really hope I'm wrong about that, otherwise I will consider avoiding the Arena for the future, as a good option for my own sanity. Why? Because it's hard already to fight against top teams, besides the fact that they have a very good crafted defense, the system boosts their chances to the max already and, right now, after a few Relics on board, most of them will be pretty invincible to the vast majority of the players (the only option will be to watch how your team is wiped out in 25 seconds).
Like I said, I hope that I'm wrong, but for a few weeks ago I started to not enjoy the fights in the Arena, mostly due to the inequity the system is making.
Surely, if & when the iron coins will be available from some other sources, the situation might be balanced again. And we're gonna be back to square one, like it was said in a previous post.